Itchy and Scratchy
Appearance
Itchy and Scratchy is a TV show inside a TV show (Krusty the Clown) inside a TV show (The Simpsons) inside a TV show (The Tracey Ullman Show).
Ultra violent cartoon (usually watched by /Bart and /Lisa) depicting a cat and mouse continually attacking and mutilating each other with all sorts of deadly weapons.
Itchy and Scratchy is possibly a parody of the old but popular cartoon, Tom and Jerry or, perhaps more likely, of the more recent Ren and Stimpy. The orignal episode, Steamboat Itchy, was a parody of Mickey Mouse's original Steamboat Mickey.