Heathcliff is challenged by a dog and in the crowd you see the Catillac Cats: Riff Raff, Mungo, Hector and... a very disturbing version of what's SUPPOSED to be Cleo (with the pink leg warmers).
Well apparently the Catillac Cats crew: Hector, Wordsworth and Mungro, were created specifically to appear in both the Main Segment and the Secondary Segment of the show. Riff Raff was an original design and never intended to appear on the Main Segment.
This crossover leads me to believe it was either a jab at the creator of Riff Raff or vice versa. Either way, it shows that Heathcliff IS top cat if ya got Catillac Cats cheering him on. Go Heathcliff!
This youtube video was linked to Izlude's Google+ Timeline