Corrected entry: Kramer walks into Jerry's apartment to get a Pepsi and tells Jerry that he would get Jerry's watch back (the one that Jerry threw away). Jerry then goes to Kramer's apartment door. When Kramer leaves Jerry's apartment, he has the Pepsi in his right hand. When Jerry tells Kramer that he had thrown away the watch, the Pepsi can is gone.
Corrected entry: Russell doesn't know that Elaine knows Jerry and George. This is apparent when Russell tells her about a pilot with a "new young talent, Jerry Seinfeld." So why doesn't he figure it out when there is a character named Elaine Benes in Jerry's show?
Correction: I don't remember Russell ever saying he didn't know that Elaine knew Jerry and George. Furthermore what would be the problem if he did? Elaine dated Russell, but she never conned him and it wouldn't have likely changed anything about the situation. As for the character in the show, I don't think they actually referred to the characters by their full name. I believe Elaine's character was just referred to as Elaine.
Correction: There was a promotion being run, for which you had to spot the Pepsi can in particular episodes and send in a postcard pointing out when you saw the Pepsi can.