When Dipper and Mabel hear rumors that a lake monster lives at the bottom of the local lake, they enlist Soos to take them on a boating expedition to prove that it really does exist, instead of going with Stan Pines to go fishing.
The episode starts in the morning at the Mystery Shack. Dipper and Mabel are eating breakfast and decide to have a syrup race with "Mountie Man" and "Sir Syrup," their ornamental syrup bottles, when Mabel taps the bottom, giving her an advantage, and she wins, yet ends giving her a cough at the syrup. Dipper then reads up on a magazine called Wacky News, and comes across an advertisement for a monster photo contest. An advertisement for a human-sized hamster ball on the opposite page catches Mabel's eye, but Dipper tells her he was actually talking about the monster photo contest. He asks Mabel if they got any pictures of the gnomes from the previous episode, but they did not. However, Mabel did state that she kept a piece of a gnome's beard. Stan walks in and says that it's family bonding day. Dipper asks if it's going to be like their last family bonding day where he had them make counterfeit money, and they were sent to the County Jail. Mabel said it was so cold and shivers. Stan admits he hasn't been the best summer caretaker, but he swears they will have real family fun today. He then exclaims joyfully that the kids have to put on blindfolds and get into his car. They both cheer and throw up their hands, but then Dipper realizes what Stan just said, and says "Wait, what?" in confusion.
Dipper and Mabel are blindfolded in the back of Stan's car. Dipper says blindfolds never lead to anything good. Mabel feels like all her senses are heightened and that she can see with her fingers, then starts rubbing Dipper's face. Stan is driving recklessly, and Dipper asks him if he's wearing a blindfold too. He says he might as well be with his cataracts. Stan asks if the fence on the edge of the road is a woodpecker, and they barrel roll down a hill. They arrive at their location, and Stan tells them to take off their blindfolds.
It's fishing season at Lake Gravity Falls, and the whole town is out. Dipper is curious as to why Stan wants to bond with them all of a sudden. Stan says that he's never had fishing buddies, because the guys from the lodge don't "like" or "trust"' him. Suddenly, Old Man McGucket runs past, telling everyone that he saw the Gravity Falls Gobblewonker again. (This is when Blendin Blandin can be seen picking up a calculator to the right of the screen.) He shows everyone a boat that has been broken in half and claims that the Gobblewonker did it, but he is ridiculed by the townspeople and his own son for it. Dipper realizes that if they can get a picture of the Gobblewonker, they can split the $1,000 photo contest prize money 50/50. Mabel fantasizes about what she could do with $500 and has a fantasy of getting the giant hamster ball, and gloating to a hamster. She then scurries around, smashes through the wall and rolls away chortling happily. Mabel then stops at a crosswalk and talks to two 80's cartoon-style-boys in a sports car opposite her, saying "You can look, but you can't touch!" The boys' sunglasses fall off as they say "Awesome!" Mabel, then rolls away squeaking, while techno music plays in the background. Mabel comes back to her senses and she says she is 1,000,000% on board with Dipper's plan. Soos pulls up and says they can use his boat, The S.S. Cool Dude, for their monster hunt, and the twins ditch Stan and head off to Scuttlebutt Island.
On their way to the island, Dipper gives Mabel and Soos a quick lecture. He says the number one problem with monster hunting is camera trouble, so he has bought 17 disposable cameras. They soon lose six out of their seventeen cameras. Afterward, they decide that Dipper will be captain, Mabel will be co-captain and Soos will be associate co-captain. Mabel uses a pelican as a ventriloquist's dummy, then attempts to do so while drinking water (which she chokes on, scaring the pelican away). On the boat, Dipper says they'll lure the Gobblewonker with fish food in a barrel. Soos asks permission to taste the fish food, Dipper says "permission granted," Mabel says "permission co-granted." and Soos says "permission associate co-granted" and licks the fish food. Soos makes a face and Mabel and Dipper start laughing. Soos says "Dude, I don't know what I expected that to taste like." Once they land on the island, they hear "monster noises" and rush to check it out. They believe they've spotted the Gobblewonker, but it turns out to be a colony of beavers that in their language, say unusual, charming phrases. One of the beavers has a rusty chainsaw that when bitten, makes the "monster noises" that the twins and Soos heard earlier. Dipper then realizes that the rock he is sitting is actually the tail of the enormous Gobblewonker, and gets ready to snap a picture, but the Gobblewonker then begins to chase them on dry land.
They make it back to the boat, but they are still being chased in the water. Finally, they end up going through a waterfall and into a cave. The Gobblewonker gets stuck in the cave hole and Dipper begins taking pictures. A piece of the cave lands on the Gobblewonker and Dipper notices that something is wrong when sparks fly out of the creatures' joints. He knocks on the Gobblewonker and realizes that it is made of metal. They open the trap door revealing Old Man McGucket. McGucket reveals he made it to get attention for his son because when you get old, you have to go through a lot to spend quality time with your family. It is admitted that Old Man McGucket creates robots for revenge when he gets neglected. Dipper and Mabel then realize that shouldn't have ditched Stan. They later meet up with him and apologize. They take some family photos then relax and enjoy the boat ride. The camera angle then goes underwater and we see the actual Gobblewonker eating Dipper's last camera.The end credits show Mabel, once again, imitating the pelican and telling a joke to Dipper, which annoys him.
- Written by:
- Directed by:
- Storyboards by:
- With the Voice Talents of:
- Additional voices:
- Jennifer Coolidge as Lazy Susan
- Grey DeLisle as Rosanna and Hank's son
- John DiMaggio as Manly Dan
- Will Forte as Tyler Cutebiker
- Will Friedle as Reginald
- Alex Hirsch as Old Man McGucket
- Chris Parnell as Host
- Kevin Michael Richardson as Sheriff Blubs
- Justin Roiland
- Horatio Sanz as Worker #1
- Gregg Turkington as Toby Determined
- Conrad Vernon as Tate McGucket
- Jason Ritter as Charlie (uncredited)
- Casting by:
- Dipper mentions their encounter with the gnomes in "Tourist Trapped," and Mabel presents some gnome beard hair she's saved.
- An advertisement for the Tent of Telepathy displaying Gideon Gleeful is shown on the back of Dipper's magazine, foreshadowing his debut in "The Hand That Rocks the Mabel."
- Stan states Ben Franklin looked like a woman, foreshadowing the secret documents found in "Irrational Treasure" that confirm he was, in fact, a woman.
- Blendin Blandin from "The Time Traveler's Pig" is seen picking up Mabel's calculator.
- Xyler and Craz, the boys that appeared in Mabel's imagination of the human-sized hamster ball, later appear in "Dreamscaperers."
- The Gravity Falls Gossiper, which appears in "Headhunters," reported on Old Man McGucket's homicidal pterodactyl-tron.
- Viewership: This episode was watched by 3.136 million viewers on its premiere night.
- This was the first episode of the series produced.
- This is the only episode with an end tag that stretches across the entire screen during the credits.
- On the Disney Channel website, the episode's title is shortened to "The Gobblewonker."
- Stan is revealed to have a vanity license plate on his car that reads "STNLYMBL," which is most likely short for "Stanmobile," as Alex Hirsch says that "the wrong name" is on the license plate.
- Wendy was absent in this episode.
- During the end credits of this episode, the cryptogram reads "QHAW ZHHN: UHWXUQ WR EXWW LVODQG." Once decoded, it reads "NEXT WEEK: RETURN TO BUTT ISLAND."
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