Bart gets a Hindenburg-themed checkbook from the bank, and it has the words "Oh, the humanity!" printed on top.
Krusty's off-shore banker is modelled on actor Sydney Greenstreet, particularly his role in this film, owing to the line "Oh, it's too hot today!"
The "haunted house" the family stay is an exact copy of the Bates home.
Comic Book Guy mentions a "Doctor Who" marathon.
The name of the show is on a bus driving by Krusty's house.