The episode title is a parody of the hip hop group Insane Clown Posse (as is Krusty's line to "get down with the clown," which, in Insane Clown Posse culture means, "to be a fan of the Insane Clown Posse.")
In addition, Krusty when doing his USO Comedy Tour was seen holding a golf club, referring to a trademark of real life USO comedian Bob Hope, where he often has a golf club with him on the stage during his sketches, where he always makes a swing whenever his jokes are well-received.
Coincidentally, the relationship of Krusty and Sophie reflects on the animated Christmas special, Olive the Other Reindeer because Dan Castellaneta (the voice of Krusty) also voices the postman in the special and Drew Barrymore (the voice of Sophie) also voices the titular character, Olive. Also, the special was created by Matt Groening himself, the creator of the Simpsons, who also did a sound bit as an elf for the special.
During the poker game, Homer starts to sing the chorus to the The Lion Sleeps Tonight. Fat Tony then threateningly tells him not to sing it.
When Krusty stops Erin from assassinating Saddam and she retaliates by strangling him, she is mysteriously wearing red shoes. This may not be a goof, but wearing such bright red shoes in the situation, defeats the purpose of having camouflage.
When Krusty goes to give Fat Tony Sophie's violin, the case has a sticker on it with her name, but when Krusty and Homer go to steal it back, the case is stickerless. Fat Tony could have torn it off after he takes it.
Stephen King somehow knew Marge's name, despite Marge not telling him who she was. She could've told him in a previous book fair.