Velma's mother says she ordered Sumatran Rat-Monkeys from Skull Island. This is a illusion to the movie Dead Alive (1992), while Skull Island was also the name of the island in King Kong (1933), as well as in the live-action Scooby-Doo (2002) movie.
At the Charity Auction, one of the people in the audience resembles Cass Elliot, who guest starred in The Haunted Candy Factory (1973) as herself.
The restaurant, "The Crab Net of Dr. Calimari" is an allusion to the 1920 movie, "The Cabinet of Dr. Caligari", which has been referred to as the first true horror film.
The auctioneer resembles David Dickinson, English antiques expert and host of a number of TV shows revolving around auctions.
Daphne stands near a statue of Cthulu in the Museum of Oddities.