The Note

... and remains at the top of its comedy game until the end of season six. At that point, Larry David began to lose interest and left at the end of season seven to pursue other projects.

In this season opener, Jerry tells Elaine and George that you don't have to pay for a massage if you can get a note from a medical professional indicating that you need physical therapy. In that case it is covered by insurance. The strange part is that Jerry goes to his dentist rather than a doctor for a note saying he needs physical therapy and gets one for both George and Elaine at the same time. This gets the dentist in trouble for possible insurance fraud.

It's a perfectly crafted half hour of comedy with nothing more than the issue of the validity of the dentist's note, Jerry's masseuse thinking that Jerry wants to kidnap her child, George feeling massively insecure about his masculinity, and Kramer's side story about seeing Joe DiMaggio in "Dinky Donuts". The chemistry and rhythm between the four main players is just perfect for the entire episode.