I've rewatched the first two seasons of Friends and so far I've found these plots that kinda ring a bell if you see what I mean.
1) Phoebe gets more money from her bank than she deserves and the harder she tries to give that money back the more money she ends up with...
2) Rachel finds out about Ross' love for her at the same time that Ross gets involved with another woman.
3) Rachel dates a Ross lookalike...
There were a couple others but I didn't write them down...