Pet rats were kept at the studio in the hallway for more than a year so that the animators could study the movement of their fur, noses, ears, paws, and tails.
To find out how to animate the scene where the Head Chef is wet, they dressed someone in a chef suit and put him in a swimming pool to see which parts of the clothing stuck to his body and which parts you could see through.
In France, where this movie is set, the movie broke the record for the biggest debut for an animated movie.
Marketing tie-ins proved problematic for this movie, as no food product company wanted to be associated with a rat.
The ratatouille dish prepared by Remy is the alternate variation called confit byaldi, adapted by film consultant Thomas Keller. This variation differs much from the conventional ratatouille in terms of preparation and method. The significant difference is that the vegetables are sliced thinly and baked instead of cooking them in a pot.