Here’s the premise: I will name a minor character from a TV show, one that is rarely seen, if ever, and maybe mentioned by name a bit more than that, and you tell me the show he/she/it is from. Special consideration needs to be taken for characters that, while might only have one or two appearances, are essential to the plots of those episodes and so are known much better (like Zathras.) As an example of what are good and bad minor character choices, here is a list:
Good:
Dr. Mickhead (Scrubs)
Bad:
The Todd (also Scrubs)
Good:
Naomi Wildman (from ST: Voyager)
Bad:
Reginald Barclay (from ST: TNG) (I realize he might actually only have a small number of episodes, but he is essential in them and is a memorable character.)
The guy at Springfield Nuclear Power Plant who can’t speak English and is responsible for anything that goes wrong. He lost the key to Marge’s office, and he was promoted ahead of Homer.
IRL Art Donovan was a member of the old Baltimore Colts football team who made many hilarious appearances on Dave Letterman’s show, talking old school about the old days, but I don’t think that’s who you mean.