Episodes where they "crossed the line" for you
Here's my list:
1) Kramer wearing odd shoes and struggling to speak, being mistaken for a handicapped man.
It was in such poor taste.
2) Jerry complaining about Puddy and George "stealing his move". Having to see George basically under the blankets "going down" on a girl was repulsive.
3) Basically anytime Jason Alexander was shirtless.