Complex sentence: The film first begins with Buster, who likes to sing and dance instead of doing his job to hunt animals, which causes Buster's owners to notice and makes a deal with one of Mix Max's henchmen to stuff him, in which they do.
Split into simpler sentences: The film first begins with Buster, who likes to sing and dance instead of doing his job to hunt animals. His owners notice this and make a deal with one of Mix Max's henchmen to stuff him, which they do.