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.
Yeah, I think that was the joke - but his "dirty talk" was so off that it veers into pedo-ish territory. But like the OP was saying, maybe ages even more poorly now given his dating past...
I'm sorry to say that 1) made me laugh, but it was the fact that everyone automatically assumed Kramer was disabled that was funny, not the apparent 'disability'.
I agree with the poster who said that Susan's death was a bit harsh. Not the death itself, but the way the characters, particularly George, just shrugged it off.
I know I probably shouldn't laugh, but I never thought I was doing so at anyone with a genuine disability. To me the joke was the false perception; the fact that Kramer was accidentally behaving like someone who had a disability, and since he was so gormless and child-like anyway, he just went along with it, almost innocently.
But it's been a long time since I saw that episode, and maybe I wouldn't find it so funny if I saw it now.
At first it's was funny, he's walking with weird shoes and unable to talk properly and says to share the cab. But he needed to be uncovered for the joke to work out. Otherwise it was "hey, Kramer is acting retarded, it's hilarious!"
I do think the joke would have been funnier if the truth was revealed and the people he'd unwittingly 'fooled' started chasing him down the street in anger, whilst he was trying, unsuccessfully, to run away in those shoes.