What shows have recycled the same plot line over and over?

"Curb Your Enthusiasm" has used "So and So thinks that So and So is cheating on So and So" several times.First in the original pilot where Larry is with Jeff's mistress and an old lady friend of Cheryl's thinks that he is cheating on her.They also used it in the only episode I have yet to see ("The Massage") with Cheryl thinking that Larry is cheating and again in "Club Soda and Salt" with Larry thinking that Cheryl is cheating on him with her Tennis partner.

Three's Company, when one of the roommates misunderstands a converation.
I Love Lucy, Lucy asks Ricky for something (usually to get into show business), he says no. She goes behind his back with some kind of wacky plan that always ends with her in trouble. Ricky usually bails her out and they live happily ever after until the next episode anyways.
Both shows were very successful and have stood the time of longevity so plot is doesn't mean as much as the talent and writing.

There was an episode of All In The Family where Archie enters Joey in a Beautiful Baby Contest, against the wishes of Mike and Gloria.
It was almost identical to an episode of The Jeffersons, when George and Louise enter Jessica in a Baby Calendar Contest, again...against the wishes of Lionel and Jenny.
Plots are recyled often. I guess it's bound to happen. There are only so many ideas after all. :)

Yes, plots are recycled often. Recall the Seinfeld episode when George and Jerry were about to embark on writing a sitcom. Jerry said to George "writer? What writer--you're not a writer!" George snickered and said, "It's a sitcom! Who needs to be a writer!?" LOL. Then later George was tying to impress a woman in a bar by telling her that he was a writer. She asked him what he writes. When he told her "a sitcom" she laughed in his face and walked off. Then she joked with her friend about what George had told her. :p I thought the 'stick out tounge' thing might work for either George or the snitty broad. Take your pick. :lol: