Remy: What is that?
Emile: I don't really know.
Remy: You don't know... And you're eating it.
Emile: You know, if you muscle your way past the gag reflex, all kinds of food possibilities open up.
When Collette asks, "What did the customer say?", there is no ladder in front of the stove. Then right before Chef Skinner tastes the soup, he is able to pull out a ladder from the front of the stove.
Near the beginning of Ratatouille, when Remy is in the sewers and begins to make his way up to the skyline of Paris, he is startled by a barking dog in one of the apartments. If you pause and look at the silhouette of the dog, it greatly resembles Doug the dog, from the 2009 Disney/Pixar release Up. Obviously another precursory nod to an upcoming movie by the geniuses at Pixar.