- Author Existence Failure: According to some members of the show (see below), the show was cut short due to Mel Blanc's failing health. Curiously Blanc still performed several voices after the series up until his death however.
- Blooper: The Catillac Cats episode "High Goon" uses a Heathcliff title card (specifically the one of Mungo about to step on a sunbathing Heathcliff).
- Creator Backlash/Old Shame:
- Although this show is often looked back with fondness and nostalgia for those who grew up in the 80s and early 90s, most of the people who worked on this show don't have very nice memories of it. John Kricfalusi (The Ren & Stimpy Show and The Ripping Friends) considered the show to be just another mediocre '80s series; Scott Shaw!note (Captain Carrot and His Amazing Zoo Crew!) found DiC too disorganized; one writer talked about Executive Meddling from Japanese animation producers, as TMS, or rather their subcontractors, opposed wacky cartoonish gags; and Chuck Lorre (Two and a Half Men) found this show beneath him because he hated cartoons. Even more extreme, Eddie Fitzgerald (Tiny Toon Adventures, the basis for Pinky and John K.'s protege) doesn't remember ever working on this show despite his name being in the credits, which has been speculated to be because he prefers it never happened.
- The only aversions were the voice actors. Donna Christie said that this was her favorite series, and the rest of the cast enjoyed working on the set.
- International Coproduction: Between DIC Entertainment (USA and France) and TMS Entertainment (Japan) for the first season.
- Keep Circulating the Tapes:
- Various VHS and DVD compilations (mostly of the Heathcliff segments) were released up until in the mid-2000s, all of which are now out of print. Shout! Factory released the first 24 episodes before losing the rights to the series. Mill Creek Entertainment released the entire first season on DVD, one half in 2012 and the other half in 2013. Finally averted in August 2016 when Mill Creek released the entire series on DVD, including the previously unreleased second season episodes.
- The most recent print of Heathcliff: The Movie was released on DVD in 2004, though it can be found on YouTube
- Off-Model: Sometimes, Wordsworth's skates would disappear from his feet in between shots; it's especially noticeable at the start of the episode "Junk Food". In Season 2, Hector's ears would sometimes be colored beige (they're normally black), and then there's Cleo where sometimes her entire being was drawn horribly, such as in the episode "Hector's Takeover".
- Screwed by the Lawyers:
- Ever wonder why Heathcliff and Riff-Raff never meet outside the end credits? Heathcliff's owners at the time, the McNaught Syndicate, apparently didn't want characters not created by them appearing with Heathcliff, so hence Riff-Raff and Cleo were both unable to appear; Hector, Wordsworth, and Mungo were created specifically so they could appear in both segments.
- The Catillac Cats segments are referred to as "Cats & Co." in the credits due to a lawsuit from Cadillac.
- Talking to Himself: Riff-Raff and Wordsworth were both voiced by Stan Jones, and then there's Mungo and Leroy, both voiced by Ted Ziegler.
- Urban Legends: Popular belief is that Heathcliff and Riff-Raff did interact with each other at least once in the show. Often times, someone will claim or swear in the internet that they saw an episode where they actually meet, sometimes adding that they heard the episode only aired once for whatever reason. Actually, no such episode was ever made, and the only time the two characters interacted was during the end credits and an odd cameo from Riff-Raff in the comic strip. However, this belief is so strong even today that it will not probably fade anywhere soon (see Common Knowledge in YMMV).
- What Could Have Been: Per an interview with voice actress Donna Christie, the second season would have been longer had it not been for Mel Blanc's failing health.
Trivia / Heathcliff and the Catillac Cats