I loved it when Ross said "It doesn't matter who came on to who"
and Joey replies "whom." That was so unexpected and a complete turn of roles. Remember that episode in season 5 (TOW Joey's Big Break I thinkl) when Phoebe was pissed at Ross but she couldn't remember why and he did that trick on her, but Monica suggested she might be mad at him cause he always corrects people's grammar: "whom, whom, SOMETIMES IT'S WHO!"