Flatchoo appears in the beginning of the movie, in a seperate line of toys called the Belch Brigade. His appearance is a red large orge-ish looking character. When pressing his stomach he produces burping and farting noises.
Even though in the line of toys produced after the success of the movie he is considered a Gorgonite, he is not actually one of the Gorgonites but only part of the Belch Brigade line. The toy comes with an additional character, Nibble, who is not seen in the movie.