Continuity mistake: When Remy and Emile are cooking the mushroom on the roof, notice that the mushroom is skewered on the antenna. When Remy and Emile are hit by lightning and sent careening off the roof, the mushroom is instantly on a stick in Remy's hand, instead of the antenna. It could've been sent flying by the lightning bolt, but even if it was, there was no stick in the previous shot for it to have ended up on.
Continuity mistake: In the beginning of the movie when the crazy lady goes after Remy and Emile with the shot gun, she fires three shots at them: two in the wall and one towards the ceiling when Emile is crossing the banister. After Emile crosses the banister, look at the ceiling around the chandelier in the next shot. There are already 4 shotgun holes in the ceiling.
Continuity mistake: In the beginning when the crazy shotgun lady is after Remy and Emile, she knocks over the umbrella canister when she pulls out her shotgun. Watch for that canister as the scene progresses. It goes from being knocked over to being upright and back to knocked over during the scene.
Continuity mistake: When Remy and Emile are cooking the mushroom, Remy has it skewered on the antenna on top of the house. The end of the antenna part that Remy is using has a piece on the end that sits perpendicular to the part Remy has the mushroom on. It would've been really hard for him to get the mushroom on there without it breaking, and in the shot it looks intact to me.
Deliberate mistake: Main headlines in newspapers appear translated for each country for the kids to understand it, but the rest of the news appear in English, despite the movie taking place in Paris. Also, most signs -such as the poisons in the window shop- have labels written in English.
Continuity mistake: Right before Anton Ego eats the ratatouille, there is a shot of the right side of his face and his left hand holding a fork with the ratatouille on it. Very close to his left hand, in that same shot, is also a glass of wine, a lamp, and a small pot of flowers. Then right before the image zooms away from him into his flashback in the next shot, after eating the ratatouille, the shot shows a glass of wine and now a bottle of wine next to his left hand, while the lamp and pot of flowers moved closer to his right hand.
Continuity mistake: When Linguini is exiting the pantry after just being confronted by Skinner, the light from the kitchen illuminates Linguini's hat, revealing a silhouette of his hair. Remy's silhouette is not seen. A shot from inside the hat shows that Remy is sitting upright, not even trying to hide in his hair.
Continuity mistake: When Rémy crashes through the window, the cookbook appears to contain only about 10 heavy pages. They don't look like clumps of thinner pages, which might be the case if they were wet, but they aren't. The animators seem to have drawn the pages in a hurry since they aren't a plot point yet. Later in the sewer, when Rémy meets "Gusteau", even though the book has been soaked during the trip, it now is animated with hundreds of normal pages, and they are inexplicably dry.
Continuity mistake: At the beginning of the film, Remy and Émile are at the old lady's house. The cooking show comes on TV. In one shot, the TV is facing straight forward, sitting perfectly parallel to the edge of the cupboard. In the next shot, the TV has moved to the left and is sitting at an angle. Watch its relation to the edge of the cupboard.
Continuity mistake: When Colette is fleeing Gusteau's after Linguini reveals Remy, she skids to a stop at a red light, sliding between two rows of several cars. However, a few moments later when the light turns green, there's a row of cars stuck behind her where there wasn't room for them to have been before.