When Kramer comes into the restaurant with the clipboard, Elaine reaches for it. In the next shot, she is already writing on it.
At the end, Elaine, says she cannot afford two of them (sponges) when her boyfriend, Billy, implies if they can go for another round of sex. When in reality the sponge can be inserted up to 24 hours before sex & needs to be left in place for at least 6 hours after sex. So as long as you don't go over wearing a single sponge for over 30 hours, Elaine could have slept with him again without sacrificing another sponge.
Elaine buys a case of the recalled sponge at the pharmacy. It would seem no reputable pharmacist would sell a recalled product. However, it wasn't recalled - it was taken off the market.
When Elaine stomps on George's foot, she misses and hits the floor, but he reacts to it anyway.