Trivia: At the theater Clayface is watching "The Terror" a movie starring Jack Nicholson, who played the Joker in 1989's Batman.
Suggested correction: More likely, this is a reference to Clayface's origin in the comics, where he was an actor who starred in a film called "The Terror," then dressed as its killer and killed the cast and crew of a remake set to be made without his involvement (his shapeshifting powers coming later into his character's life). This is evidenced by how the film on the projection screen appears to be a black and white film from the 30s-40s, matching Clayface's first appearance in comics.