Garfield and Friends (1988)

S2E10 The Sludge Monster

When their car breaks down, Jon, Garfield, and Odie find themselves stuck in a creepy, deserted hotel. To pass the time, Jon decides to have some fun and pulls a prank on Garfield and Odie, claiming that a "sludge monster" roams the halls of the eerie building. The two pets, spooked by Jon's story, start to imagine all sorts of spooky scenarios as they navigate their unsettling surroundings.