Combined with Fix Fic, there's a number of 9 fics where the dead Stitchpunks are brought back to life somehow or other Stichpunks are found, sometimes the two are combined and lead to OCs getting paired with characters like 5 and 6.
Tadashi surviving the fire is the fans' most-asked What If?. The most common solution is that someone saved him, he used one of the inventions from the SFIT Showcase to protect himself, or Callaghan kidnapped him for some reason. These are usually followed by a tearful reunion with Hiro and Baymax.
Stories where at least one team member gets kidnapped are pretty popular, with Hiro being the most popular, since he's basically everyone's little brother. That said, Fred sees some popularity as a target given that his family's wealth would logically make him a target for kidnap-for-ransom even without the superhero business; a fan-favorite reason for his kidnapping is for someone to tempt him into a procedure to give him superpowers and for it all to go sour. In stories where Hiro and one of the other team members get kidnapped together, the villains like to pull I Will Punish Your Friend for Your Failure to force Hiro to do their bidding; this can also be done with Cass, alive!Tadashi (who may get the same threat right back at him) or even a civilian as Hiro's fellow prisoner.
Crossovers with Rise of the Guardians where Tadashi is resurrected as a Guardian with fire powers, similar to Jack coming back with ice powers after drowning in a frozen pond, are fairly popular.
Miguel developed the ability to see and interact with ghosts after the events of the film. Cue antics with his deceased family... or more frightening plot elements; take your pick.
Marco, based on the original concept for Miguel, becoming a part of Miguel's life. Sometimes he's a total jerk and the pair are longtime enemies but most of the time, the pair become friends though it varies if Marco starts off as a sweetie or if he grows into someone Miguel can befriend. Marco is usually Ernesto's descendant and hates it unless he stays an antagonist, in which case he idolizes the man and hates the Riveras for "stealing his well-earned reputation".
Ernesto shows up to kidnap Miguel; cue the dead Riveras being after his sorry bony body. Sometimes Miguel's significant other gets dragged along for the ride.
AU fics surrounding Hector's death are a plenty. Ranging from "what if he survived his poisoning and managed to get home to Imelda and Coco" to "what if some little deviation meant Ernesto was proven to be Hector's murderer around the time the act happened".
Villain Hector. Sometimes they are straight up swap with him getting Adaptational Villainy and Imelda being paired with Ernesto while other times Imelda and the other Riveras join Hector in his villainy, in which case Imelda was usually the brains.
Protagonist Coco, where Coco finds out the truth about Hector. Sometimes she's an adult while other times she's a child.
Hector and Imelda were friends with Naveen and Tiana from The Princess and the Frog. The exact timeline can vary but usually Naveen is able to protect Hector from the outcome of Ernesto's poisoning attempts and Lottie quickly bonds with Coco, with Naveen and Tiana joining her in doting on the little girl.
Disney Princess-themed works usually have the Princesses (and often times characters not officially in the franchise, like Alice or Esmeralda) hanging out in a castle, cabin, or other large building together.
The Disney's Hercules fanfiction community has stories introducing Persephone, the Goddess of Spring and the traditional Queen of the Underworld, into what is most often a sequel to the movie. She and Hades always get their mythology canon Happily Married status by the end. The Trope Codifier for most of these was probably Hope Springs Eternal.
Given that it is already The Theme Park Version of Greek Mythology, certain parts of the story considered unsavory to modern palates (such as Persephone being both Hades niece, daughter of Zeus and Demeter, and a teenager) are reworked or ignored according to the wishes of the author. The whole abduction and marriage situation is either turned into more of a mutual decision between the two, for Persephone to escape her My Beloved Smother, or kept intact and made to work with the movies interpretation of Hades as a suave villain full of schemes.
Persephone, though stuck in a couple of background scenes for the movie (pink-skinned, blonde curls, huge petal hat), is nearly always given original looks and personality depending on what the author wants to see or feels fits with Hades already established character.
There are fanfics for Incredibles 2 where Violet's Satellite Love Interest, Tony Rydinger, either avoids getting mindwiped or regaining his memories of her through some means. Alternatively, he can find out Violet's secret without regaining his old memories.
Many fanfics basically make interpretations of how a sequel to the movie would be like, revolving around Riley's issues during puberty.
There are also fanfics that involve Riley dying and her anthropomorphic emotions saying goodbye to her. Usually, these have old age as the cause of death, but one of them had it be cancer, but still had Riley as an elder.
A common trend in fanart shortly after the film was released involved drawing "fusions" of the anthropomorphic emotions to symbolize the combined memories from the end of the movie, like Joy and Sadness fusing into a "Melancholy" or "Ambivalence" being.
The fandom seems to love the plot of dragging a kid from the present and befriending Littlefoot and the gang. In fact, any plot that falls anywhere on the Speculative Fiction spectrum, with the fate of the world in Littlefoot and the gang's hands, is common.
Having an army of Sharpteeth invading the Great Valley is common.
Fan-works revolving around any of Ariel's sisters.
The Lorax has many a fanfic detailing how Granny Norma came to know the Once-ler, sometimes having them be lovers in their youth. Some of these take it a step further and have Ted come to the realization that the Once-ler is his grandfather.
Back in the Once-ling days, the Lorax fandom was often ridiculed because of the prevalence of Once-ler self-cest/Oncest. For a few years, shipping the Once-ler with alternate universe versions of himself was very popular.
Though not that predominant, many fanfics of Pinocchio involve either giving Stromboli, Honest John and Gideon, and the Coachman their own comeuppances, or simply have them as the main focus of the plot.
Fanfics seem inordinately fond of direct retellings of the movie, except this time there's a plucky female recruit/stowaway/cabin girl who's a Kindred Spirit to Jim and thus can fall in love with him over the course of the story, if she isn't his sister instead.
Fics where Jim goes on a voyage that is essentially the same as the voyage to treasure planet, accompanied by a female stowaway who is either essentially Jim's personality from the movie (while Jim can play Older and Wiser) or your average Tsundere so she and Jim can have a Slap-Slap-Kiss romance.
First there was a ton of "real life gamer gets sucked into the game world" fics.
Turbo/King Candy comes back as an evil glitch, and plots revenge only to be redeemed by / falls for Vanellope.
Sugar Rush gets an upgrade, aging Vanellope into an adult so she can be shipped with Ralph.
A new game opens in the arcade, featuring a lonely character who can be a love interest for Ralph.
Another of the same cabinet is added to the arcade. Fics usually involve either 'twins' or the characters memories being wiped.
"An arcade cabinet gets shut down" fanfics. It's usually a death fic but sometimes the characters do live in limbo. Even worse are "The entire arcade gets shut down" fics where it's impossible for anyone to survive.
A random karter liked Vanellope and was bullying her in a childish way of expressing it — these stories are popular. It's usually Taffyta or Rancis.
Vanellope really was a glitch and died at the end.
Taffyta trying to make amends with Vanellope for her bullying towards her after she has regained her memories of her.
Fics exploring the consequences of magic returning are popular, with popular consequences being "Ian is bullied for his role as a returner of magic and the first known wizard in centuries", "Ian is kidnapped because of his magical abilities; Barley has to come to the rescue without magical back up before Ian runs out of time" (the latter can feature Ian having to rescue a kidnapped Barley, with the threat of Barley's captors hurting or killing him hanging in the air, or both boys being kidnapped so their captors can use Barley's safety as leverage to force Ian to comply with their demands, in which case Laurel is the one coming to the rescue, usually with Bronco) and "ancient forces of some kind are unleashed and it's up to Ian to save the day, with at least his family's help and possibly some new friends".
Also popular are A Us where Wilden was actually revived and got to spend his one day with his sons doing more normal things.
Slice-of-life stories where Ian gets his first crush are seeing good popularity.
Stories featuring humans coming in contact with the creatures of the movie's setting are rapidly gaining popularity, though the reverse (Ian and/or Barley ending up in the real-life world) is well-liked too.
While it's still gaining speed, some fans are fascinated with a version of the movie's world where magic never went away, instead evolving as society did.
"Ian messes up a spell or casts one without thinking about the consequences; the fallout causes major problems" is also quickly showing itself to be well-liked as a plot.
On the flip side, stories where Cornelius gets kidnapped, either as an adult or as Lewis, see decent popularity; they're usually a case of Kidnapped Scientist but ones where he's kidnapped as an adult can also be for ransom or revenge for marrying Franny.
On the more mundane side, stories that deal with Wilbur's apparent lack of academic ability are decently common; they vary on whether or not he's actually Book Dumb or just sees himself that way (with a few having him be just as intelligent as his father but with a relationship that got strained by the events of the "dark day at the Robinson house").
Stories where Wilbur uses the time machine to hang out with Lewis, both in the latter's native time period and in the future/Wilbur's present, are very popular; plot lines vary wildly but one of the more popular ones is "Wilbur gets stranded in Lewis' time period and hangs out with him while they try to fix the issue that's stranding him".
Not overly popular, but there are several stories where an additional character with ties to Wilbur (often a friend, but sibling is also a possibility) is part of the movie's plot, often playing the voice of reason to Wilbur.
The Iron Giant: by far, the most popular fic plot involves the Giant returning to Rockwell to be with Hograth, though the exact plot varies between fluff and drama; this plot is so popular in fact that it is often treated as "so definite I don't even point it out" in stories with other plots.
"How exactly did Annie and Dean's courtship go?" is a popular story element and while it's not to Recurring Fanon Character standards yet, it's near universally believed that if Hograth ended up with a half-sibling, it would be a sister.
Kent Mansley escapes prison and seeks revenge on Hograth for him losing everything.