The numbers reflected on Stan's face while he is turning on the portal are not mirrored.
Agents Powers and Trigger switch seats during the scene where they locate the source of the "readings."
When Wendy enters the shack at the announcement of the after-party, she is wearing her name tag. However, when she is leaving with the crowd, her name tag is not seen.
When Dipper and Mabel are in the attic, the rind on Mabel's sweater disappears, and when Mabel is claiming that there is nothing left to discover about the Journal, there are only watermelon seeds on the neck and sleeves of her sweater; the front of the sweater is completely missing the watermelon seeds.
In the shot where Dipper says he doesn't know why he tells Mabel things, his nose isn't properly colored.
Grenda smashes the Stañatas and the mess is all over the floor; however, it disappears in the shot where Candy, Grenda and Mabel are dancing.
When Lee, Nate, Tambry, and Thompson arrive at the party, Lee is wearing a sleeveless shirt. In the next shot, it has short sleeves. When all four are seen dancing, he is sleeveless again.
In the shot of the teens dancing, Tambry is wearing her regular day wear instead of the party outfit shown earlier.
Lazy Susan's lipstick is missing when she enters the Mystery Shack during the party. Later, her lipstick reappears during the scene when the zombies emerge from the ground, but disappears again in the next shot.
In the journal, the incantation's second line reads "Diablo Dominium," but Dipper reads it as "Diablo Dominus."
The karaoke machine changes places, and even disappears, many times when the zombies are starting to attack the shack.
There are some colored lights hanging around the Mystery Shack in a shot behind Soos when he starts approaching the twins with the zombies. The lights are not present in any of the other shots.
In the shot where Dipper and Mabel are backing away from the zombies, the flower in Mabel's hair disappears, then reappears in the next scene.
When Stan sees himself in the reflection of Journal 1's hand, the reflection is not reversed.
During "Taking Over Midnight," when the three are singing "We're queens of the disco!", Dipper steps up, followed by Mabel and then Stan, but when the camera zooms out, the order changes to Dipper, Stan, and then Mabel.
After singing "Taking Over Midnight," Stan's fez appears while yelling "Deal with it, zombie idiots!" It then disappears again in the next shot.
At the end of "Taking Over Midnight", when a zombie tries to attack Dipper, all of the microphones are suddenly gone.
Stan activated the Universe portal in "Gideon Rises" by pushing the lever in front of it to the left. But during a full shot of the portal room at the beginning of this episode, the lever is seen facing the right.
Wendy briefly has two left arms when she reaches for some popcorn.
In the same scene, in one frame, Dipper's mouth is completely displaced from his face.
When Wendy first notices the map of Gravity Falls that covers the tunnel entrance, the map is only about a square foot in area. In the next shot, the map is at least twice that size.
In the scene in which Dipper is going to find another way out of the bunker, he grabs Wendy's right hand. In the following shot, he is holding her left hand.
When the Shape Shifter drops Journal 3, Dipper walks up to the Journal and picks it up. In one frame, the Journal lifts itself closer into Dipper's hands without Dipper touching it yet.
When Wendy tears off one of her jacket's sleeves, she tears off at least a foot of cloth. When she puts her jacket back on at the end of the episode, the torn sleeve is only a few centimeters shorter than the untorn one.
At the end of the episode, Dipper and Mabel are sitting in the middle of the log, but when Soos sits down, they are suddenly on the far right of the log.
After Soos draws the w-neck, the marker he used disappears from his hand.
When Dipper explains Mabel's talent in mini-golf, Stan is snacking on his Stan-cake while holding the fry pan. The pan disappears in the following shots.
As everyone enthusiastically rises to go to the golf course, Waddles is sitting on the floor. But after the shot of Soos joining in, Waddles is sitting on the couch.
In one frame, when Dipper is trying to hit the ball, his mouth disappears.
When Mabel runs over to the end of the eighteenth hole to see if her ball went in, she does not have her putter with her. In the next shot, she suddenly has her putter, which she angrily throws down. The putter disappears again in the next shot, only to reappear when Pacifica approaches the Pines.
When Pacifica insults the Pines family, Dipper does not have a putter, but in the next shot, he is leaning on a putter.
When the golf course manager announces that the course is closed, one of the wings on the golf cart he is driving passes through a pole.
Dipper does not have a golf club with him during the scene where Mabel is practicing the eighteenth hole, but suddenly has one after he notices a noise inside the windmill.
When Dipper first hears noise coming from inside the windmill, the wood covering has a design on it. When he approaches with Mabel to tear it off, the design is gone.
When Dipper takes off the panel of the windmill, he's to the left of Mabel. In the next shot, he is to the right of her.
The map of the course is not an accurate representation. For example, the windmill and the pirate ship are close together, but in the map they are widely separated.
The pirate captain's eye patch covers his left eye when he uses the spyglass, while in other shots it covers his right eye.
When Pacifica and Sergei enter the course at night, the part in Mabel's hair is on her left, but changes to the right in the next shot, then changes back the left in the shot after that.
When Dipper, Mabel and Pacifica have escaped the Lilliputtians and the golf cart collapses outside of the golf course, one of its wings is undamaged. However, in the next shot, both wings are torn off.
When Mabel is apologizing to Pacifica, in one frame, her braces are visible over her mouth when it is closed.
Dipper's mouth disappears for a frame.
Dipper suddenly has a putter.
The pirate ship is between the Dutch hole and the Castle.
But in the map, the castle is in between the pirate ship and the Dutch hole.
When Mabel is playing the keyboard in the scene where Dipper, Mabel, Soos and Wendy are making puppets, the bottom half of her leg is cut off.
After Bill tells Dipper he's been keeping an eye on him, Dipper's eyebrows and eyes continuously appear and disappear.
Before Bill forms the screaming head, his hand is cut off for one frame.
When Gabe visits the Mystery Shack, Mabel's braces disappear when she laughs nervously.
In the scene in the attic where Bill offers to unlock the laptop, the password bar on the laptop disappears for a shot, then reappears in the next shot.
When Bill drinks a can of Pitt Soda, the cap is already off before he opens it.
While Bill is speaking to Soos outside the Mystery Shack, Bill's eyes disappear in one frame.
In the theater, Wendy and Bill are sitting in the same seat at first, with exactly one free seat to their right. In the next shot, they are sitting in two separate seats and there is still a free seat to their right.
Wendy, Soos and Stan are sitting in the front row, with Bill's empty seat between Wendy and Soos. When Gabe sits down, they're not seen in the front nor the second row, but when the show is about to begin, they're sitting in the second row, in places previously occupied by other people. Wendy is 2 seats away from the aisle and there's no empty seat beween her and Soos. Later, when Gabe is watching the show, Stan, Soos and Wendy aren't where they were in the previous shot. The location of several people around them varies between all these shots, like the woman with the red handkerchief on her head, or the man with the strapped blue overall.
When Gabe meets Mabel in her dressing room, he is carrying some flowers. In the next shot, he has his puppets on both of his hands and the flowers are nowhere to be seen.
After the intermission, the guy in the blue overall is sitting in front of Wendy and at least 4 seats away from the aisle, with a woman with glasses sitting at his right. Gabe is not seen. But when "Bipper" is pulling Mabel up, Gabe is in the front row right next to the aisle, with the second seat free, the man in the overall sitting in the third one and the woman with glasses isn't there. Wendy, Soos and Stan aren't behind them, and many other people change places too. These kind of changes continue for the rest of the episode.
When "Bipper" is chasing Mabel around the stage, the front row is empty.
Sometimes there's an aisle in the middle of the theatre, dividing the seats, but sometimes there are aisles only in the sides.
When Soos runs into the gaming store, the box he finds Romance Academy 7 in isn't visible.
The note on the back of Romance Academy 7 disappears for a shot, then reappears in the next shot.
When Mabel suggests Soos see some real girls, there are cans of Pitt Cola on the floor that weren't there in the previous shots.
During the scene where Mabel and Dipper drag Soos away from his room, Mabel's cheeks have outlines on them for two frames that flicker back and fourth.
The "HE's GOT ATTI-CUBE!" poster in the door of Soos' room shows a prominent COOLCUBE logo in the upper right corner. When Soos takes the Romance Academy 7 disc and leaves for his date with Melody, the COOLCUBE logo is missing.
When Soos is talking to Melody for the first time, despite the fact that she's in the foreground in one shot, Soos's arm moves over her hair.
In the scene where Soos and the others are hiding behind the toppled arcade cabinet, the character peeking over the fortress wall on the side of the cabinet changes from a peach color to red in one short scene.
In Hoo-Ha Owl's Pizzamatronic Jamboree, the graphics for Star Battle appear on the unit for First-Person Puncher.
Everything is pixelated.
There is no box.
The box has appeared out of nowhere.
The sticky note is gone for a shot.
No soda cans
There are suddenly soda cans on the floor.
Mabel's cheeks have an unusual outline around them for two frames and flicker back and forth.
While Stan is attempting to get the traveler to come into the Mystery Shack, his mouth overlaps his nose for a frame.
When Stan is attempting to get the traveler come inside, his mouth disappears for one frame.
When the Pines first approach the Hand Witch's table, the stall in the background says "Lots O Pots." Later, it changes to "Pots Aplenty."
When Stan mocks Dipper's concern about a curse, the stalls in the background change. Instead of Lazy Susan and Old Man McGucket's stalls, Pots Aplenty and Cheep Cheep Tires appear. Additionally, they are transposed (Pots Aplenty is on the right of Cheep Cheep Tires next to the witch's stand).
When Waddles shows Dipper and Mabel the What-the-heck-ahedron, the computer and cup of coffee he knocked over a few shots earlier are gone.
When Waddles shows Mabel the Smarticle Accelerator, the ladder Dipper was standing on is gone, and Dipper is standing in mid-air. In the next shot, he is suddenly on the ground, and the ladder has reappeared.
In the shot where Waddles starts the Smarticle Accelerator, Dipper's pose changes from standing straight to having his hands in his pockets without any animation.
Robbie's memory tube disappears from the insertion slot in the shot after Dipper puts it in.
When McGucket spots the tube with his memories, the label is on the side facing towards him. When he grabs it, the label is on the opposite side of the tube. It is later shown that the tube is only labeled on one side.
In the shot where Mabel is entering "SUMMER ROMANCE" into the memory gun, her hand is not turning the dial.
The date in this episode is shown to be July 13th, Soos' birthday. However, in Journal 3, this episode is said to take place sometime between July 29th and August 22nd.
The candy that Soos takes out of the vending machine is not seen in the machine.
In the first shot of Soos' driver's license, his signature has three stars above it and a lightning bolt to the right. In the next shot, there is only one star and the lightning bolt is to the left of the signature.
The bandage on Stan's hand is missing in every shot except for when he enters the front yard at Soos' birthday party.
In the first wide shot of Mr. Zzz's Mattresses, the man at the far right of the shot has two left arms.
When at the Heart-A-Tap Dance Studio, Toby Determined's reflection in the mirror shows him much closer to the wall than he actually is. In addition, his mouth is misplaced and the railing in front of him is not reflected.
When Abuelita has a plate of cookies, they are shaped like dinosaurs. Later, when Soos has the cookies in his room, they are shaped like circles.
When the twins and Blendin are taunting each other just before beginning Globnar, Lolph is at first on Blendin's right and Dundgren is on his left. In the next shot, they have switched places. They switch to their original positions in the following shot.
In the images of Blendin chasing the twins on a giant clock and of the wheel barrow race, Mabel is missing her braces.
When Time Baby asks Dipper and Mabel to choose Blendin's fate, Blendin suddenly has handcuffs on, which were not present in the previous shot.
Dipper and Mabel only tell Soos that they "got caught up in [...] time travel," that there was a time cyclops and a time race, and that they think they know how to fix his birthday. In the same dialogue, Soos knows more than what he should: he says that they battled through time and space in gladiatorial combat just to get him a wish.
The candy Soos gives the twins.
The candy is not in the actual machine.
Soos' signature in the first shot
Soos' signature in the next shot
Stan's bandage is missing.
Toby's reflection is much closer to the mirror than he actually is and has a misplaced mouth. Also, the railing is not reflected.
The plug jack of the phone Wendy uses to explain Woodstick is see-through.
When Dipper, Mabel and the teens find Robbie in the grave, the pine tree on Dipper's hat is missing in the bird's eye shot.
When Stan is sewing the rainbow wig onto the taxidermy gorilla, the can of Pitt cola is gray. It turns pink in the next shot.
In the shot where Stan is aiming his crossbow, the bandage on his hand is colored black.
When Stan grabs his crossbow and aims it at the hot air balloons there are other weapons in his toolbox. But when he talks to Soos, the toolbox is empty.
The picture of Robbie as a little kid is different from how he was shown in "Blendin's Game."
When the teens are congratulating Dipper for thinking of taping snacks to Thompson, Wendy says "Well done!" without moving her mouth.
When the teens are in Thompson's garage, Dipper, Tambry and Wendy are sitting on boxes arranged in a semicircle. When Lee picks up Dipper, the boxes are in a straight line. They then shift back to their previous positions in the next shot.
When Tambry sits down in the booth at the diner, she puts her purse on the ground next to her, but in the next shot, it is gone.
When the Love God enters the diner, there are a few frames where he has two chins.
When Tambry eats the love potion, her hair is pointed to her left instead of the usual right.
When Robbie and Tambry leave Greasy's Diner, Robbie's black belt turns blue.
When Mabel shows the teens her happiness chart after Robbie and Tambry fall in love, the drawing of Lee is not fully drawn for a frame.
Nate's mouth disappears for a frame after he hears about Tambry dating Robbie.
When Mabel is looking through Love God's potion belt, the order and color of the potions changes. Mabel then takes the black anti-love potion, but it's still in the belt when Love God starts running.
When Stan is looking at the drawing of the Stan balloon, his bandage is missing.
When Stan's hot air balloon rises, it has no basket, but in subsequent shots, it does.
The appearance of the Northwest Manor is different than when it was seen in "The Golf War."
When sitting in the recliner watching TV, there is a pizza box next to Dipper, but in the next shot it's gone, replaced by a can of Pitt Cola.
When Dipper answers the door when Pacifica arrives, he is wearing his socks. When he agrees to help her, he's wearing his shoes.
Grenda has two ponytails for a few frames before she makes the truce with Candy and Mabel.
When the ghost laughs and his beard blazes before he tricks Dipper into releasing him from the silver mirror, his mouth overlaps his nose.
Candy drips cheese onto the pastries, but later, when she is talking to Mabel, there is no trail of cheese near the fountain or on the pastries. Also, the pastries' appearance has changed.
The lumberjack's ghost tells Dipper that they were asked to build the mansion that same day, 150 years ago, but the course —which says he will return in 150 years— was casted years later, after the mansion was finished. This means that either the ghost returned before 150 years had passed from his death (when he casted the course), or the lumberjacks were asked by the Northwests to build the mansion more than 150 years ago.
When Grenda approaches Marius von Fundshauser to pretend that something is on his shirt, a yellow stain can actually be briefly spotted on his shirt.
Only a few people are holding glasses of apple cider before Preston Northwest gives a toast, but after Preston's glass breaks, everyone is holding a glass.
The wooden people change positions several times.
When Dipper is turned into wood, his bow tie isn't tied. Later, when Pacifica looks at him, his bow tie is tied. When he turns back to normal, his bow tie is untied again.
Northwest manor in this episode
Northwest manor in "The Golf War"
Pizza box replaced by Pitt Cola can
Dipper just has socks on.
Dipper is suddenly wearing shoes.
Cheese on pastries
No cheese on pastries
Mouth overlapping nose
Dipper is nowhere near the rest of the people and his bow is untied.
Dipper is now with everyone else and his bow is tied.
When Stan insists on being included in the fireworks party, Dipper and Mabel switch places from one shot to the next.
When Dipper takes a popsicle out of the cooler on the roof, the cooler lid is closed.
When the Pines are admiring the fireworks Mabel set off, the cooler disappears for a few frames.
Throughout the scene wherein the Pines are playing with fireworks and water balloons, Stan's jacket is buttoned and unbuttoned from shot to shot.
When Agent Powers is telling Dipper and Mabel about the doomsday device, Dipper and Mabel switch places from one shot to the next.
Stan's bandage disappears for a few frames when he hands the taxi driver money, then reappears in the following frames.
Journals 1 and 2 switch places when Dipper is theorizing about Stan having stolen the journals from the author.
While assembling the Universe portal blueprint with the journals, Dipper opens Journal 1, but the portals pages shown inside are Journal 3's. (Journal 1 has the bottom part of the plans, while Journal 3 has the top left.) After reading the blacklight warnings on the blueprints, Dipper flips through the bottom Journal, which, as the shot wherein Dipper arranges the blueprints would indicate, is Journal 3. However, the pages through which he flips are not present in Journal 3.
When Dipper reads the black light messages in the portal's pages in the journals, he says "I was deceived, and now it is too late." This line is not one of the messages seen.
During the entire climax sequence in the underground portal room, the door from the lab to the portal changes between open and closed multiple times.
Dipper and Mabel switch places.
Next shot: jacket is buttoned
There is no message reading "I was deceived, and now it is too late."
In "Not What He Seems," the left sleeve of Stan's coat is ripped by a tree branch. However, in this episode, the tear isn't seen.
Stan's bandage disappears after Ford punches him. It only reappears after Ford questions him about who knows about the portal.
In Anomalous Phenomena, the book of anomalies that Ford reads in college, the pages with the two-headed ducks and cats call the condition "polycephany," when it is supposed to be spelled "polycephaly."
When Dipper screams excitedly when Ford mentions writing the Journals, Stan has a cleft chin like Ford's.
When Stan lights his match to burn Journal 1, it is facing Ford. In the next shot, it is facing Stan.
Ford deceives the recently memory-wiped agents, Trigger and Powers, using a few of Mabel's drawings as decoy paperwork. While doing so, the crayon text "What hath science wrought?" on Mabel's self portrait vanishes and reappears.
When Dipper explains the rules of Dungeons, Dungeons, and More Dungeons to Mabel, Mabel's sweater collar turns purple for a shot.
Many other errors occur during Mabel's letter writing. After Mabel writes, "Just yesterday, gravity reversed itself, almost destroying the universe and totally wrecking the whole town!" it cuts to the TV. When it cuts back to Mabel, that portion of the text has disappeared and Mabel is writing, "But the coolest part of the summer was when Grunkle Stan's twin brother came out of this portal thingy" in the place the text was previously. In addition, Mabel says "Now we have two Grunkles for the price of one!" but doesn't actually write it down, but when in cuts to her picture, it is written next to it. Furthermore, the ink that the pen uses is clearly shown to be purple, until it zooms in on her picture, where the pen writes in blue ink instead.
When Stan staples the turkey head onto the beaver's body, his burn mark is on the left side of his back.
When Stan is showing Mabel his taxidermy of Duck-tective, he has a cleft chin for a shot.
In the scene wherein Dipper and Mabel are in the attic at night and Dipper is designing his dungeon, Mabel is wearing a headband, which disappears for a shot, reappearing in the next shot.
When Mabel, Stan, and Grenda find Dipper and Ford playing Dungeons, Dungeons, and More Dungeons in the TV room, Ford only has 5 fingers on each hand.
Tyler and Sprott throw their hats into the ring, but in the next shot, they are both wearing their hats.
At the mayoral replacement meeting, Bud Gleeful punches in the picture of the Mystery Shack on the Gravity Falls map, but in the next shots, the map is intact.
Robbie is seen sitting with his parents and Tad Strange at the back of the town hall during the meeting, when everyone starts yelling "election!" Robbie is suddenly up at the front row sitting with the Pizza Guy and Lazy Susan.
Soos wears a blue suit at the beginning of the radio interview scene, but when the telephone rings, he is wearing his normal attire.
When Soos falls to his knees after Mabel uses the mind control ties on him, the word "STAFF" on the back of his shirt is missing.
When Dipper reveals to Stan that the ties were made to control him, both ties are exactly the same.
Before Mabel gives Stan the "OUR HERO" sash, there is a mug on top of the fish tank. After Stan takes the sash, there is a shrunken head in place of the mug.
Stan puts on the sash Mabel knitted for him upside down, but once it's on him he's wearing it right side up.
When Mabel jumps off her chair after Ford tells her that he needs unicorn hair, a second pair of her legs are still shown on the chair.
At the end of the scene where Ford shows Dipper his study, the switch on top of the Project Mentum helmet is silver. In the following scenes, it is black.
When Dipper puts on the helmet on Ford's head, the repeat of the thought "I miss Dimension 52" is misspelled as "I miss Dimention 52."
When Ford and Bill are talking at the end of Ford's flashback, Ford says, "just call me, a friend". When he says, "just call me" he is shown shaking hands with Bill using his left hand, but when he says, "a friend" he is shaking with his right hand.
When Dipper and Ford are talking after Dipper tries to erase Bill out of Ford's mind, Ford only has five fingers on his left hand when he tells Dipper that he would have done great were Bill really there.
A symbol in the cryptogram is misplaced on the ancient wall Ford finds, making the word decode to "FOOJISH."
When Ford grabs Dipper, he drops the Rift and the Memory Gun on the floor, but in the next scene both the Rift and Gun are no longer on the floor.
When the girls return to the shack with the unicorn hair, Wendy's left eye is swollen from fighting the unicorns, but when Ford says to Mabel that she's a good person, her right eye is swollen instead. When Stan runs in, her left eye is swollen again.
Lee and Nate change the board outside of the school by rearranging the letters in "SAWDUST INHALATION DRILL- 8:00 GO FIGHTING BEAVERS!" to "NO ESCAPE." However there is no "C" or "P" in the former message, so they wouldn't have all the letters needed to write "NO ESCAPE."
When Dipper climbs out of the trench made by the droid, he picks up his walkie talkie off the ground. Scattered next to it are a flashlight, a pen, and a small notebook. In the next shot, the three objects are gone.
After releasing the rift, Bill, while possessing Blendin, removes Blendin's goggles to reveal his eyes and then collapses as he leaves the body. However, in the next shot, Blendin is again wearing his goggles.
When Bill leaves Blendin's body, Blendin's body falls and lands on top of the broken pieces of the glass orb that used to hold the rift. The next shot shows Blendin's body laying beside the glass orb's remnants.
When the citizens of Gravity Falls notice the arrival of Bill, Lazy Susan has both eyes open, which can't be done without her holding her lazy eye open with her hand.
Blendin is lying on top of the glass.
Blendin is lying next to the glass; Blendin is wearing his goggles after Bill took them off.