The Catillac Cats

The group is headed by Riff-Raff, a tan, short, tough, streetwise alley cat.

In the flashback episode "Christmas Memories", it is revealed that Cleo is, in fact, one of the Catillac Cats herself, even going as far as to indicate that she coined the name.

[3] On more than one occasion, Riff-Raff ends up "two-timing" Cleo with another female cat (accidentally or otherwise).

[4] Although both Heathcliff and The Catillac Cats are set in the fictional city of Westfinster, only Hector, Wordsworth and Mungo appear in both segments.

Riff-Raff appears with Hector and Mungo in a crowd cheering for Heathcliff in season one, episode nine.