Cowboy BeBop at His Computer: Animation historian Jerry Beck claimed in his book The Hanna-Barbera Treasury that this series "featured the Ant Hill Mob as [Penelope's] chief rival". Probably never seen an episode before in his life (or watched Wacky Races instead).
Uncredited Role: In the "Voices" section of the end credits, Paul Lynde is nowhere to be seen. This is because his agent recommended it not be listed (in this as well as The Cattanooga Cats, where he voiced Mildew Wolf in the "It's the Wolf!" cartoons) as it would hurt his credibility. Even though everyone knew it was his voice to start with.
What Could Have Been: An early sketch for the series featured Penelope's younger brother, Johnny Pitstop, who had Dastardly and Muttley as his bodyguards.