That had actually been one of the planned subplots on MWC. The sweet Rhodeses thought they would improve the Bundys, but the Bundys ended up corrupting them. Which is how these things usually work in real life.
Al & Marcy were the perfect foils for each other.
I think the 500 pound shark stinking up this topic is The Fonz.
Mimi from Drew Cary paid for all of the wasted screen time in the episode guest starring Joe Walsh as Drew’s guitar player in the series of episodes when he was considering leaving the store to be a full time accordian player.
Walsh spent an entire scene staring at Mimi, and when Drew spoke to Mimi, Joe exclaimed “My God! you see her too?”
That was going to be my choice as well. She was cool girl at first and then became a harpy and everyone acted like that was just her. 
Yes! I was coming in here to say, “What about Monica?”
She starts off as funny with a hint of neurosis, self-deprecating but usually amusingly so…and then turned into this emaciated shrieking creature.
The episode where Joey’s girlfriend doesn’t want to hang out with them because she thinks Monica is annoying and loud and Chandler is boring was fairly accurate as to how outsiders would’ve seen them.
Han Solo did drop in Return Of The Jedi.
Harrison Ford might as well have sent a wax dummy in to play the role, & stayed home eating Cheez Wiz.
One idea which was floated for a new Blackadder season was Blackadder as a present day Tory MP, with Baldrick as his secretary: this was never made, but the idea was recycled for the late 80’s/early 90’s show The New Statesman, with Rik Mayall as the machiavellian conniving Tory MP Alan B’Stard, who had a dim accomplice named Piers as his idiot foil: it was moderately amusing and fairly successful, running to four seasons, but it was always very obviously derivative of Blackadder.
Interesting. I was pretty young when LIS was on and remember just the conceited and affected character that just seemed to be there for comic relief, like when he ingested some sort of green gas and obtained super strength as a result, which he then used to push the others around.
That’s actually the same episode. I had forgotten about that.
You forgot the worst example: Jackie. Seeing Laurie Metcalf reduced to playing such a flat, poorly written character in the show’s last years was painful.
Hal on Malcolm in the Middle was never “complex,” but he did manage to manifest the occasional instance of good judgment and fatherly responsibility. In later years, he was the stupidest, most irresponsible character on the show (including Jamie).
On Star Trek Voyager, Chakotay was interesting for about one episode, until they put him in a Star Fleet uniform and he became a bloated stiff like Riker.
Hi,
I nominate Nate Fisher, Jr. in Six Feet Under … started out kinda goofy, “stands up for what’s right” guy and ends up to be a total, horrid sleazeball. OTOH, Brenda went from totally unsympathetic to admirable for putting up with Nate.
I used to dread the rumours that someone “major” was going to die towards the end of the show but by the last three episodes I was praying it would be Nate.
At least Riker had a personality. Chakotay quickly became Janeway’s bitch, and never really escaped from that role, although hooking up with Seven of Nine helped restore his manhood a bit.