Trivial Pursuit Cards
Trivial Pursuit has a number of references to Clue.

The above pictured card asks:

"What suspect in the game of Clue teaches College?
The answer: Professor Plum

Other cards ask:

What are the six murder weapons in the game of Clue?
The answer: Candlestick, knife, leadpipe, revolver, rope, wrench

What game room is on a Clue board?
The answer: A billiards room