Inspired by the Mrs. Columbo (1979) post the other day, Leighton did a little research into spin-offs and found this ultra-rare special. It was created by and featured Lorenzo Music in his role as Rhoda's besotted doorman, Carlton, now in a new position as a doorman in a seedy hotel.
The show is extremely hard to find. I've only been able to locate one source for it. Toonarific.com has copies available, though the price is quite steep - $100. Above and below are a few screen grabs from it.
This extremely rare special, produced by MTM productions has never made it to a commercial DVD release. It's not available for viewing online that I can find. The factor number should really be 11 or 12 for this one.
Obscurity factor: 10 (extremely rare and hard to find, not on DVD or YouTube, no online video available)