Was this only a phenomenon of '70s sitcoms?

It happened at least once in the Eighties too. There was a Family Ties episode that had Michael J. Fox alone on a bare soundstage, the premise being that he was having a session with a psychiatrist following his friend's suicide. The whole ep was a monologue by Fox. Probably a bit of a vanity thing, but it might also have been that the producers wanted to showcase the dramatic abilities of a star player. It was never a device that was used frequently, but it did seem to occur mostly in sitcoms from the Seventies.

I noticed that trend too. I think it started with Archie when Edith was sexually assualted. I hated it when a sitcom delved into drama. I just wanted to watch a comedy not being preached to and that's what it felt like.

I call it an overbearing star's ego trip
My thought's excatly


I thought P.E.T.A. meant People Eating Tasty Animals

It depended on the ability of the actor. I don't need a comedy to always be nothing but mindless laughs--some drama is welcome, but not all actors can pull it off. I thought the Alda monologue was good, but Bea Arthur's Maude one was too self-indulgent and 'actorish'--a good comedienne, but way OTT when trying to be 'dramatic'.

I don't know of any other examples but I will always remember that episode of M*A*S*H* for the following reason. My grandmother had never seen an episode of the show so she sat down and watched the Hawkeye monologue story. After it ended she said "Is that all that series is about that man talking all the time to himself. What a ratbag! Talk about overrated! I'm never going to watch that show again." And she never did.

I always thought the episode where they use camera as if it was a patient. Watching from his bed at whats going on. Is by far the worse M*A*S*H*episode.

Fox was a genius at comic timing but his gift at drama always seemed underappreciated. So it was a good choice to showcase his less recognised side. I still remember that episode.

But Alan Alda's ego and delivery was too overbearing.
I didn't care for the "One Day at a Time" vanity either.

~
“Hawdd yw hi, i fod yn ddewr o tu nôl i mur.”
🐉

It was done as recently as in the Family Guy episode "Brian and Stewie' (S8 Ep17) http://www.imdb.com/title/tt1582289/?ref_=ttep_ep17. Although there are 2 characters in the story, both are voiced by Seth McFarlane.