This a list of unseen characters who exist within Gravity Falls, but have not properly appeared in the series.
Auldman "Old Man" Northwest was the father of Preston Northwest, grandson of Nathaniel Northwest, and the grandfather of Pacifica Northwest. He was the patriarch to the late 20th century. During his investigation of the Northwests' fraudulence, Ford Pines attempted an interview with Auldman, but was forcefully removed from the family's grounds before he could get the chance.
Beatrice isa woman who once slapped Stan Pines for "being a cad."
Sandy Trembley was the third wife of Quentin Trembley back in the 17th century. She is mentioned when he and the Pines Twins try to get out of the wooden box while hearing a woodpecker, Quentin thinks it sounds her (implying that she may of been one too).
.GIFfany's creators were the various programmers of the game Romance Academy 7. When programming the game the character .GIFfany eventually gained sentience. The programmers unsuccessfully attempted to delete her, and in response she "deleted" them.
Jeffrey Cannuck is a victim of the Blind Eye Society'smemory erasing. Based on where his memories are stored, it can be inferred that he knew notable information about Gravity Falls' supernatural side.
Mr. and Mrs. Chiu are Candy Chiu's parents. At one point, Candy spoke to her mother about having a sleepover with Mabel. Later, it's revealed that every last week of summer vacation, Mr. and Mrs. Chiu force their daughter to attend music camp. 
The Queen of the Manatees is Mermando's fiancée, whom he pledged to marry to avoid an undersea civil war. She is not mentioned until the last known letter of Mermando is delivered to Mabel Pines, and the engagement likely took place after he met Mabel.
Mr. Ramirez is Soos Ramirez's father, Abuelita's son-in-law, and Reggie's uncle. Soos has not seen his father since he was at least four years old. Soos realized the extent of his father's neglect on his twelfth birthday, which led to a decade-long disdain for the date. In "Weirdmageddon 2: Escape From Reality," since he's never seen his dad, Soos fantasizes that he has the body of a pro wrestler and a face he once saw on a hot sauce bottle.
According to Alex Hirsch, Soos' father is Caucasian while his mother is Hispanic.
Soos' Spanish-language surname, Ramirez, suggests that he took his mother's surname.
Abuelito is Soos Ramirez and Reggie's late grandfather and Abuelita's former husband. According to her, he is "not [in heaven]."
Mrs. Ramirez is Soos' mother, Abuelita's daughter, Reggie's aunt (and therefore the sister of one of his parents), and Mr. Ramirez's wife. Little is known about her, aside from the fact that she is of Latino heritage.
Nate's girlfriend is mentioned in "Boyz Crazy" by Robbie when he says that Nate and her were going up to Lookout Point, though they never showed up. In "Double Dipper." Nate was seen dancing with a girl that might've been her.
Is the father of Marius von Fundshauser. He died when Marius was only seven-years old, during the time his son inherited a cravat and an epaulet factory that quickly gained prominence among the richest of the rich in his entire home area.
Wax John Wilkes Booth is one of several wax figures from the episode "Headhunters." He is a wax figure of the infamous actor and assassin of President Abraham Lincoln. When Wax Abraham Lincoln is found melted, Stan accuses Wax John Wilkes Booth of having done it.
Wax Abraham Lincoln was one of several wax figures from the episode "Headhunters." He was a wax figure of the American President during the civil war, who had melted due to the fact that someone left open the window letting the sunlight in and Stan then turns towards Wax John Wilkes Booth, thinking he was culprit behind it and holds him responsible.