Alternate Character Interpretation: It is possible to see Stanley as not so benevolent troll, considering he dreams of a land where all trolls are essentially copies of him (even if supposed to be "good") and, in the end, he covers New York in vegetation. Whether he is simply delusional or actively malevolent is up to the viewer.
Ass Pull: Gnorga discovering Stanley's activities in Central Park by hearing the sounds of Rosie's crying.
Big Lipped Alligator Moment: The boat ride suddenly enters Stanley's dream land which he apparently created out of nowhere, we see all kinds of happy things that have no relevance to the story, and when the sequence is over, nobody mentions it again.
Broken Aesop: The first time we see Gus and Rosie, Gus is selfishly screaming and fussing that he wants everyone to do the things he wants to do for a change, even wrestling with his parents as they struggle to get to work. After all the drama in Central Park has passed and the kids are finally home, what does Gus ask his Dad when the latter offers to take them all out for the day? To do what he wants to do. (Granted, the intent was to return to the park in hopes of reviving Stanley, but it does little to show how Gus has come to outgrow his own brattiness.)
Idiot Plot: Gnorga banishes Stanley all the way to New York City, without even knowing what Llort meant to suggest, and she banishes Stanley to New York City, far removed from the trolls' domain. On the kids' side, they only get themselves involved because the housekeeper neglected to keep a closer eye on them, so they freely walked out of their own apartment without anyone noticing. Later, Stanley is only discovered to be enjoying his exile because Gnorga just happened to be hearing Rosie crying out of all the babies who are crying at any given time, and she still goes to end him even though Stanley can no longer threaten her reign over the trolls.
Inferred Holocaust: The movie ends with all of New York being engulfed in vines and flowers. It's meant to be heartwarming, but ends up looking like some sort of supervillain takeover, or a scene right out of Life After People. It's not even made clear if it's just supposed to be another dream sequence.
Glurge: Stanley's vision of a "perfect" world, even more so than everything else in the film. Basically, it's a sickeningly-sweet world filled with trolls who all look and think exactly like him.
There's a scene in Gnorga's Villain Song wherein she turns a bat to stone. It's worse than it sounds; one would expect her to just touch it and have it turn to stone then fall, right? Wrong. Instead one of its wings turns to stone and it desperately tries to flap away while the rest of its body slowly starts to turn to stone as well. The poor thing perches on a skull and desperately tries to escape...and then its entire body turns to stone. And then it blinks.
Nightmare Retardant: It's very hard for Gnorga to look threatening when she's chasing Gus and Rosie on a tiny little tricycle.
No Yay: Stanley's reaction when Rosie, a toddler, kisses him. He seems waaay too happy about it.
Rooting for the Empire: The villains of the film, Gnorga and Llort, are far more popular and liked than the actual protagonists, Stanley in particular.
Gus on a smaller scale. He spends most of the first part of the movie as a kind of Anti-Hero. And he's the one willing to fight for his ends, unlike Stanley, the supposed hero who would rather cower.
Ron the Death Eater: Stanley gets this treatment from some viewers, largely due to his glurge nature, not to mention the similarities between his actions in the film's ending, and the lost ending to Little Shop of Horrors.
The Scrappy: Stanley himself often qualifies as this due to his sickeningly sweet personality and cowardice. And that's not even mentioning what he apparently does to New York at the end.
Invoked by the director himself, who had hopes that Stanley could be written as a much more interesting and flawed character with a much more engaging history between Gnorga's empire and himself. Unlike his partner, however, Bluth blamed himself for hastening the production to create what felt more like a child ripped out of the womb than a finished, well-produced film.
Llort's hand waves regarding why he would rather not just let Gnorga stone Stanley would have made for a fascinating subplot, which would give Stanley additional motivation for his goals as well as add complexity to the villains. This whole film is full of originality that's sadly left unexploited.
Ugly Cute: Pretty much the film's entire design aesthetic.
"Weird Al" Effect: The "I'm a Bad Troll" meme derives its melody directly from an old Russian folk song, "The Volga Boatmen".
What an Idiot: Llort is essentially responsible for triggering the entire conflict of the movie due to his pointless complaining.
Gnorga insists on going after Stanley and destroying him even though he is far removed from the troll world and now living in exile in Central Park, where his magic cannot affect the queen's realm.
Stanley's whole outlook makes him come off as this, but considering how apparently being a delusional nut job seems to work out well for him in the end...