Friends Season 6 Episode 17 : The One With Unagi (a.k.a. The One With The Mix Tape)
Rachel and Phoebe take self-defense classes. Ross, who had previously practiced karate, tries to attack them by surprise and convince them that they lack unagi, supposedly a state of "total awareness". (In reality, as pointed out by Phoebe and Rachel, unagi is just a Japanese dish.) Chandler and Monica celebrate Valentine's Day several days after the actual date because of their schedules, but they forget to make each other home-made gifts: Monic...