https://screenrant.com/sitcom-tv-show-characters-never-see/

Despite not showing their faces, these are some of the most memorable characters in sitcom history, even more so because of their mystery.

Larry’s Father & Larry’s Sister from Leave It To Beaver.
Nanny from Muppet Babies (Orginal)

Best ever unseen character is Maris Crane from the original Frasier.

One of my all-time favorite unseen characters was Carlton, the inebriated doorman on Rhoda. He had his catchphrase "Hello, this is Carlton your doorman." The producers couldn't find the right actor to voice the role so in the first episode producer Lorenzo Music filled in. He was so funny that he had the role for the show's entire run. If you watch the closing credit, he was always billed as L. Music.

Larry’s Father & Larry’s Sister from Leave It To Beaver.
Nanny from Muppet Babies (Orginal)

On the show, there was an unseen character for several years, who was always in Miss Landers' class--Angela Valentine. There were always anecdotes about her--she lost her bite plate on the playground, she threw up in the cloak room, she had a sixth toe. I think she once wore a Jackie Kennedy wig to school, and that comment by Gilbert was bleeped for many years.

Iola's parents on Mama's Family.

Face unseen, Wilson on Home Improvement. He's actually unforgettable--he was integral in the show, always a sounding board for Tim, also setting him straight many times.

Lars Lindstrom (Mary Tyler Moore)
Juanita (The Andy Griffith Show)
Vera Peterson (Cheers)
Charlie Townsend (Charlie's Angels)

Lars Lindstrom (Mary Tyler Moore)
Juanita (The Andy Griffith Show)
Vera Peterson (Cheers)
Charlie Townsend (Charlie's Angels)

I don't think Charlie's Angels was a sitcom.

https://screenrant.com/sitcom-tv-show-characters-never-see/

Despite not showing their faces, these are some of the most memorable characters in sitcom history, even more so because of their mystery.

Wilson WAS seen, albeit partially and enough so his face could be completed in my mind. Then at the curtain call during the series finale he did come out.

I can't believe nobody's posted this one yet! Howard Wolowitz's mom on The Big Bang Theory.

On M.A.S.H., when Margaret Houlihan got married (and divorced), her husband Donald Penobscot (not sure if that's the right spelling) was often talked about but we never saw him.

Ed.

On M.A.S.H., when Margaret Houlihan got married (and divorced), her husband Donald Penobscot (not sure if that's the right spelling) was often talked about but we never saw him.

Ed.He appeared in two episodes: when asking Frank to be his best man at the wedding and the M*A*S*H Olympics where his showing off lost Margaret's team the race.

Two other characters that were never seen were Steve Urkel's parents on Family Matters.

One of my all-time favorite unseen characters was Carlton, the inebriated doorman on Rhoda. He had his catchphrase "Hello, this is Carlton your doorman." The producers couldn't find the right actor to voice the role so in the first episode producer Lorenzo Music filled in. He was so funny that he had the role for the show's entire run. If you watch the closing credit, he was always billed as L. Music.

I always got a kick of him too and wondered how he kept his job being so tipsy.

10 Significant TV Characters Who Never Actually Appeared In Their Shows (https://screenrant.com/tv-notable-characters-never-appear-own-shows/)

TV shows often introduce characters who remain unseen, from Charlie in Charlie’s Angels to Vera Peterson in Cheers, an overused yet funny trope.

Seinfeld

Two of Kramer’s friends, Bob Sacamano and Lomez