This is one of three episodes where Ross tells someone his birthday. The only problem is that it's never the same day, or even month.
Rachel's hair goes from fluffy to flat and back to fluffy between shots.
When Rachel receives her paycheck, the envelope is seen to be open, yet when she comes to take the paycheck out of the envelope she is seen ripping it open.
Ross says he told everyone when he lost his virginity to Carol, and Monica even remembers the anniversary on her own. However, in The One with the East German Laundry Detergent (1994), she tells Angela that her brother never told her when he lost his virginity.
Female receptionist in the hospital is on the phone talking about a candy bar. In the picture, where her face is partly seen on the left, you can see from her lips that she is starting to say the sentence "Well I'm not completely satisfied", but you cannot hear any voice. Then immediately it is cut to a new picture where she actually says the whole sentence.
Ross, Chandler and Joey purport to attend a New York Rangers-Pittsburgh Penguins NHL hockey game in October of 1994. In reality, a labor dispute canceled the first half of the 1994-95 NHL season, and no NHL hockey was played until January 1995.
The boys go from the West Village to Madison Square Garden, but they pass a bus stop for the M15, which doesn't run anywhere near either.
In the beginning of this episode Joey and Chandler say that they've bought hockey tickets for Ross' birthday, to which he replies that his birthday was 7 months ago. However, after he looks at the date on the tickets he is shocked to see it's October 20th. Ross' birthday is October 18th, so it wasn't 7 months ago.
When Rachel is talking to her friends, the set behind them is clearly wavering when the people walk by.
Ross says he is 26 years old. In a previous episode, it was said that he was with Carol since he was 22 years old. Joey says in this episode that Ross had been with Carol for 7 years. The math doesn't add up.
When Rachel is talking with her friends from "home", she tells them she even does laundry now. Rachel doesn't learn how to do laundry until Ross teaches her in the following episode, The One with the East German Laundry Detergent (1994).