Approx 50 min into the film when Linguini has done the "special order" success, Skinner sees Remy´s silhouette right before it´s actually revealed to Skinner.
I've just watched that bit of the movie (it's at 0:49:32 on my copy); we see Skinner reacting with shock, then we see what he's reacting to (Remy's silhouette under Linguini's toque). This is NOT a slipup.
And the submitter even spelled the name of the movie wrongly; it's "Ratatouille", neither of the "T"s are doubled.