Gravity Falls has a lot of fun with this trope, often as a consequence of subplots involving the Pines Twins and young love.
As said on the main page, spoilers are unmarked.
Examples:
- In "Double Dipper", the rogue Dipper clones (sans Tracey and Quattro, who ended up fleeing and living in the woods) were defeated with Dipper and Tyrone using water. But when they rest with soda, it results in Tyrone's own demise, much to Dipper's sadness. ("The Last Mabelcorn" reveals that he still thinks about him.) In addition, Mabel loses the party crown to Pacifica Northwest and Dipper barely got to enjoy the party. But on a happier note, the party was a financial success for Stan, Mabel made new friends in Candy and Grenda and Dipper did get to bond with Wendy and Gravity Falls: Journal 3 revealed that they did dance together.
- In "The Time Traveler's Pig," the plot revolves around Dipper using time travel to prevent himself from hitting Wendy in the eye with a ricocheting ball during a carnival game, thereby preventing Robbie asking Wendy to be his girlfriend while comforting her afterwards. Dipper does ultimately succeed but in doing so, he prevents Mabel from winning her pet pig. For the sake of his sister's happiness, Dipper is forced to put the timeline back on its original track. Mabel gets her pig, but Dipper is forced to bean Wendy in the eye with the ball again and accept that Wendy and Robbie are going to be a couple now.
- In "The Deep End," Mabel spends the episode helping her new friend and crush, Mermando, escape from the swimming pool. After finding out that Mermando is a merman, she assists him in regaining his freedom and returning to his family, sacrificing the summer romance she wanted in the process. She gets The Big Damn Kiss for her efforts, but has to let him go.
- Subverted in "Boyz Crazy". Mabel kidnaps her favorite boy band, Sev'ral Timez, from their controlling agent, but is reluctant to let them go. She turns on her friends, Candy and Grenda, and lies to them in order to keep them from leaving, but a music number from the band convinces her to come clean. She releases the band into the woods so they can be free, but one line from Candy abruptly kills the Sweet portion of the ending. Although it's played straight when the Grand Finale reveals that they did survive.Candy: They won't last a week.
- "Into the Bunker": The group escaped the bunker alive and Dipper finally expressed his love to Wendy, but she turns down his affection due to a combination of the age gap between them, and an appreciation of the value of their platonic friendship. Also, Soos manages to acquire a laptop from the bunker that may give more clues to the author's identity once he manages to fix it.Dipper: Mabel, how can everything be so amazing and so terrible all at once?
- Toyed with in "Northwest Mansion Mystery." Even though Pacifica ended the curse, making it so everyone had a great time at the end of the party... and didn't die, one can only guess what happened offscreen afterwards between her and her parents, whom she disobeyed.
- Subverted in "Sock Opera". Mabel spends the entire episode working on a puppet show to impress her new crush, Gabe. She's forced to sacrifice the entire show and her chance at a relationship in order to save Dipper from Bill. However, as Gabe leaves in disgust, he begins making out with his puppets, causing Mabel to realize that this may have been the best outcome after all.Mabel: I might have dodged a bullet there.
- "Society of the Blind Eye": McGucket has his memory restored, but it is revealed he is not the author but worked with him, with the identity of the author still a mystery. However, he is happy to learn the truth and can finally recover from insanity.
- "A Tale of Two Stans" ends with Dipper finally knowing who the Author is, Stan finally getting his brother back, the government agents mindwiped and no hard feelings between Dipper and Mabel. But Stan and Ford’s relationship is still frosty, and Stan gives up on reconciliation and tells Ford to stay away from the kids. Ford is upset about Stan activating the Portal and turning his house into a tourist trap and orders Stan to leave at the end of the summer. The brothers' story also leaves Mabel worried about her relationship with Dipper. Not to mention that it's implied that Stan and Ford's parents are dead in the present, so they'll never get a chance to reconcile.
- "The Last Mabelcorn" ends with Mabel, Candy, Grenda and Wendy getting the unicorn hair (plus treasure) to protect the Mystery Shack from Bill Cipher using force and Ford telling the truth about his relationship with the demon. But Dipper is shaken by the reveal, Stan is Locked Out of the Loop and Bill plans to possess someone who doesn't live in the Shack, putting everyone besides the Pines family in danger.
- The episode "Roadside Attraction" ends with Dipper failing to find a girlfriend, Candy getting over her crush on him, the Mystery Shack being vandalized, and Soos being left behind. But Dipper does manage to reconcile with Candy, bond with Stan, gain confidence in talking to girls and (sort of) get over his own crush on Wendy; additionally, Soos finds his way out of the maze field according to the end credits.
- Played straight with the Grand Finale: The twins have to go back home and leave all the friends they've made in Gravity Falls during their summer of frightening adventures behind. In addition, the combined scientific knowledge of the Journals has been lost, (according to Gravity Falls: Journal 3, they did recover from being destroyed by Bill, but Ford later threw them into the Bottomless Pit) and Dipper has been separated from the only member of his family who truly relates to him. Also, Dipper's attempts to get a girlfriend were fruitless, Mabel never fully got an "epic summer romance" and Pacifica lost her manor. However, Bill has been defeated for good, the town and the world are saved, the Pines are hailed as heroes, Stan has regained his memories and repaired his relationship with his brother, McGucket has rebuilt his life, Soos runs the Mystery Shack alongside Melody, Gideon and Pacifica are working on being better people and Dipper and Mabel are confident in that whatever the future holds for them, they'll face it together. Additionally, Wendy gives Dipper a letter signed by everyone in Gravity Falls saying "See you next summer".
