Complex sentence: Scratchy appears as a sorcerer's apprentice (like Mickey Mouse in "Fantasia"), brandishing Itchy with an axe and attacks him, which splits him into several smaller Itchies, who then attack Scratchy.
Split into simpler sentences: Scratchy appears as a sorcerer's apprentice (like Mickey Mouse in "Fantasia"), brandishing an axe. He attacks Itchy, which splits him into several smaller Itchies, who then attack Scratchy.