4. Rachel Doesn't Know How To Spell Her Own Surname
Make your mind up, people who wrote this show. You'd think that it'd be simple enough to pick one spelling and stick with it, given that Rachel's surname is about as simple as they come. For some reason, though, nobody was capable of committing to a singular spelling on Friends, which resulted in poor old Rachel looking as though she didn't know how to spell her own name.
Although it's spelt "Green" in the credits, then, the sign on Rachel's door in Bloomingdale's has her pinned as"Rachel Greene." On Emma's first birthday, though, it's spelt "Green" on a cake box. Have some respect for yourself, Rach - we know you're not the sharpest tool in the shed, but you're not that confused.
3. Ross Doesn't Like Ice Cream/Eats It Anyway
Oh, look: another inconsistent Ross personality trait to add to our ever-expanding collection. According to the man himself in "The One Where Chandler Doesn't Like Dogs," Ross mentions the fact that he doesn't like ice cream because it's too cold. Okay, fair enough - nothing wrong with that. Still, when Ross starts going out with Elizabeth, he can be seen eating ice cream, which either means that a) somebody forget that Ross is supposed to hate ice cream, or b) somebody forget that Ross is supposed to hate ice cream.