I was watching I think "The Foundation" on tv again the other day, and it occurred to me that they sometimes do the same gags but with different scenarios in different episodes (well, I knew that but it made me wonder if they did this often).
I could think of two.
When George was in the board meeting of the Susan Ross Foundation, Jerry rings him up to go to a movie or whatever, and George asks the guy if they're going to be long. The guy says yes, and George says in a rather mournful voice "I can't go...". In an earlier episode, Elaine had to sort out Mr. Pitt's socks and also had to tell Jerry "I can't go...."
Another one, in the dealership, Jerry rings Elaine up in a rather frantic tone and Elaine goes "Who is this....?" and Jerry hammers the phone a few times. In an earlier episode, George had to call Jerry from a phonebooth, Jerry also said "Who is this....?" resulting in the same mannerism from George, hammering the phone receiver a few times.
What others were there?