Be Yourself: What he ultimately learns by the end of the movie:
I'm sick of pretending. I pretend to be a rat for my father, I pretend to be a human for Linguini. I pretend you exist so I have someone to talk to! You only tell me stuff I already know! I know who I am! Why do I need you to tell me? Why do I need to pretend?
Cursed with Awesome: What good is being a great chef with refined tastes if A) your Extreme Omnivore family thinks you're just being unnecessarily picky and B) you're more likely to be slaughtered than be allowed into a proper kitchen?
Buffy Speak: "I am not your puppet! And you are not my puppet... controller... guy!" "Appetite is coming and he's going to have a big ego! I mean Ego! He's coming! And he's going to order! Something... from our menu! And we're going to have to cook it!"
Chekhov's Skill: Linguini’s roller skating skills, which he uses to become a really fast waiter.
Determinator: Colette was willing to go through hell to become a top chef.
Double Standard: Abuse, Female on Male: Colette hits Linguini in the face on several occasions when she is upset with him. He never complains and she is still presented as completely sympathetic throughout the film. See also Slap-Slap-Kiss further down.
Face Palm: When Ego looks through Gusteau’s kitchen after tasting Rémy’s dish.
Dropping the Bombshell: Skinner reveals during a discussion with his lawyer that he is paranoid about the rat, thinking Linguine is trying to psyche him out. Skinner's lawyer notes that he had to take a second sample of Linguine's hair. When Skinner asks why, the lawyer says:
Lawyer: The first time, it came back identified as rodent hair.
Even Evil Has Standards: Despite the fact that he is an evil, selfish schemer, he takes his job as chef seriously. The only time he is willing to serve a substandard meal is when he sees it as absolutely necessary to put Linguine in his place. Too bad it backfires on him.
Large and in Charge: Subverted; Skinner is in charge of a restaurant where all of his employees are about twice his height. Then it's double subverted when you realize that his predecessor was Gusteau, who we could safely assume to have been the largest person in the room.
Oh Crap: Both Skinner and the health inspector after barging in the kitchen and seeing all the rats.
Reassignment Backfire: Skinner, trying to get Linguini kicked out of the kitchen, gives him the task of cooking a recipe that Gusteau himself said was a disaster. To his shock, Rémy quickly fixes the recipe to the point where it is so delicious that everyone else in the restaurant wants it, running the cooks ragged to keep up with orders and convincing everyone else in the kitchen that Linguini is a master chef.
Ambiguous Disorder: They never said if anything was wrong with Ego, but it's likely that he may have been suffering from depression and had become bitter over the course of time. This all changes when he takes a bite of ratatouille.
Anton Ego: (about the restaurant) "Finally closing, is it? "
Anton Ego: "More financial trouble?"
Servant: "No, it's..."
Anton Ego: "...announced a new line of microwave egg rolls, what? Spit it out!"
Dramatic Drop: He drops his pen when he first tastes Rémy’s dish.
The Dreaded: His taste buds are so hard to please that even Gusteau, Rémy's indirect mentor, couldn't do so.
Final Boss: Satiating his taste buds is Rémy's final real challenge.
Jerk with a Heart of Gold: After Gusteau's is forced to close, it's heavily implied that he helped front the money to open La Ratatouille, and he's a regular customer there. He's also one of the few people who respects and appreciates Rémy's talent even after finding out that he's a rat; he even sacrificed his job and reputation to give Rémy's cooking the praise it deserves.
Pensive Flashback: When he takes a bite of ratatouille, he instantly thinks back to his mother making him ratatouille years ago. It's safe to assume that she's the reason why he became a food critic. And all of this is done without a line of dialogue.
Reasonable Authority Figure: Even when it's revealed that Rémy was the one who prepared his dish, he was more than willing to dub him the finest chef in France (and keep quiet about the fact that they're breaking the rules about not having rats in a kitchen).
Secret Keeper: He wrote his review without mentioning that "the genius who works at Chef Gusteau's" is a rat.
Spit Take: Subverted; he suddenly stops in the middle of one to he make sure the wine he’s drinking is okay to spit out. It apparently isn’t.