We did see her in one or two episodes. She was played by Rose Marie, best known as Sally of the Dick Van Dyke show.
Damn you, I wanted to be the first one to mention Tino. Two words: Ti-No.
Mr. Donahee, always greeted by Crazy Guggenheim on The Jackie Gleason Show.
Or for that matter, Jimmy Durante’s Mrs. Calabash.
The first episode I ever remembered hearing Peggy’s mom mentioned was the one where Peggy’s family came to visit. (King Kong Bundy played her brother Irwin).
There were some great jokes describing the mother without showing her – e.g., where Al accidentally walked into the bathroom while she was bathing, and was stricken with temporary ‘hysterical blindness’ – “It’s nothing to worry about – her doctor gets it all the time”, explained one of the brothers.
At the end of the episode, a solemn text frame dedicated the show to Divine, the 300-pound female impersonator who had died recently, and looked a lot like Peggy’s mom sounded.
What that dedication made me wonder: had Divine been slated to play Peggy’s mom? That would have explained the reliance on gags in her absence (which happened to turn out hilarious).
Apparently the situation with MwC and Divine is that Harris Glenn Milstead (the man behind Divine) had been cast as Uncle Otto for that episode and would later play Peggy’s mom as Divine.
You never see the face of Cobra Commander. And we never see behind Snake Eye’s mask either, right?
Actually, I had an action figure of him wearing a clear plexiglass mask. Also, he and Destro went in disguise in the comics, once, and [spoiler]From: David Williams <asr@mindless.com>
Oops. I forgot to describe Cobra Commander’s face for all those without the
issue. Sorry about that. My first impression of Cobra Commander is that he
looks like an older hippie. He has long, about shoulder-length medium brown
hair that is pulled back into a ponytail and long sideburns. He wears large,
circular glasses that obscure his eyes and he also has a very long, fu-manchu
style moustache. He also has a prominent chin and cheekbones.
'til next time,
David Williams[/spoiler]
Mom and Dad on Cartoon Network’s Cow and Chicken were only seen from the waist up. In later shows, even their shadows terminated at the waist (and in another, Chicken finds human male and female figures from the waist up in Cow’s closet - she giggles and says “science project” and the figures are tossed aside.)
Also on Cartoon Network, Sara Bellum on The Powerpuff Girls never shows her face - she’s always shown either from the neck down or with her hair covering her face.
Actually Elisha Cook Jr. appeared a dozen times on Magnum as Icepick, Rick’s mentor. He was the veteran of over a hundred movies, stretching back to 1930 according to the IMDb including The Maltese Falcon (as a babyfaced actor).
Displaying more Magnum geekiness, “Robin Masters” was partially shown a few times in the earlier years of the series, in a Charlie’s Angels type way. His voice was the voice of Orson Welles. Personally I liked the somewhat revisionist Higgins as Robin Masters better.
Scott_plaid describes what Cobra Commander looked like under his hood in G.I. Joe #57, but in G.I. Joe: The Movie, he was revealed to be a snake-like creature under the mask. The movie created a ridiculous backstory for Cobra, where they were readying the world to be mutated into inhuman monsters, to pave the way for the underground society of Cobra-La to take over. It sucked, and the comic books wisely decided to not follow that continuity.
As for Snake Eyes, in the comics he was revealed to be a blond man who might have been handsome if not for three huge scars that cut lengthwise through his entire face. He often wore lifelike rubber masks in the comic that approximated how he once looked, and how he would have looked without the giant scars. But he didn’t look like Freddy Krueger or Spawn under there, as we were often led to believe.
How about Chuckles the Clown on the Mary Tyler Moore show?
Phyllis Diller’s husband “Fang.”
One of the dog’s next door in Garfield.
I only saw a few episodes of Touched by an Angel, but from what I remember, God – presumably the most important character – was always off-camera. Just like Charlie! 
Only I don’t think God ever even put in an appearance via speakerphone.
And “that stupid cat who lives next door” (Snoopy’s appelation) in Peanuts! Not sure if that counts for TV purposes – the cat played a role in only one of the TV adaptations, forget which one, where Snoopy gets into an off-camera fight with the cat – there, given a name, “World War II” – in an attempt to save his bird friend Woodstock (turns out that cat actually has hold of an old yellow glove).
There was an actual invisible character on Space Cases, which ran on Nickelodeon for a couple years or so. Then she became visible and her friend became invisible, for some reason.
Remembered another one: “the Gooch”, from Diff’rent Strokes. He was the knuckle-dragging bully who hassled Arnold at school.
In all the talk of MASH, we’ve neglected to mention the biggest invisible character of them all – Hawkeye’s dad.
And I should mention his mom, who was alive in season one, but later died while Hawk was a child. And the mysterious sister, who later decided not to be born at all.
Chandler Bing’s transvesite father in “Friends,” later played in one episode by Kathleen Turner!
Passion’s Aliaster Crane was a voice-and-back-of-the-head character till recently.
[QUOTE=Big Bad Voodoo Louthree huge scars that cut lengthwise through his entire face.[/QUOTE]
Which way is lengthwise on a human face?
I think Chuckles did actually appear once, filling in (without makeup) for Ted during a strike.
However, Mary threw a party once and the power went out. So you heard, but never saw, her special guest, Johnny Carson.
He wasn’t normally snake-like, he was only like that because he was given a dose of the mutagenic spores.
As bad as the movie was, though, it has some good moments, especially the opening scene. And Sgt. Slaughter beating up on Serpentor:
“This one’s for Duke!”
punch
“This one’s for me!”
punch
“And this one’s for the good ol’ U S of A!”
big punch