"The One With The Unagi" is the seventeenth episode of the sixth season of Friends, which aired on February 24, 2000.
Joey is broke but needs money fast for new head shots, so he is determined to get enrolled for another medical experiment. Since the only one is available is for identical twins, he hires fellow actor Carl to play his fictitious twin Tony. This plan then fails when the doctor tells them that the test is for identical twins and they are not identical.
Because Monica had work on Valentine's Day, Chandler tells the group that the two of them are celebrating tonight. After Joey suggests that they each book a day at one of those romantic spas, Chandler says that he and Monica have decided to make each other home made presents this year. Both Chandler and Monica however have forgotten to make each other presents. At the last minute Chandler finds a mix tape in his closet and receives a sock-bunny made by Phoebe as his gift. Monica, guilty that she gave Phoebe's sock puppet as a gift while Chandler actually put effort into making a gift, promises to make all Chandler's wishes come true in the kitchen and in the bedroom.
However, during dinner the next night Monica decides to listen to Chandler's mix tape, which had turned out to be made by Janice for one of Chandler's previous birthdays. Monica is furious and Chandler tries to make it up to her. Monica agrees to forgive him, but the tape, which is still playing, suddenly plays Janice's recorded voice, which causes Monica to storm off.
Phoebe and Rachel take self-defense classes that have them bragging about how they can kick anyone's ass. Ross tells them that after years of studying karate he has learned that self-defense is useless without Unagi, a state of total awareness. Rachel and Phoebe tell him that Unagi is a sushi and that there's no such thing, with Chandler later telling him the same thing. After Ross jump scares them, the two return the favor in his apartment. This causes Ross to sneak into Phoebe's apartment but he fails to hide successfully, as the girls notice him as they enter their home. They easily subdue him, which causes Ross to go to their instructor to ask how to fight them off, but he comes across as a man desperate to attack women, especially his ex-wife.
At the end, Ross sees the backs of two blonde-haired women near Central Perk and attacks them from behind, only to be attacked back. As he is running away from them he pauses for a second to see Rachel and Phoebe staring at him from a window at Central Perk, and he runs away in fear as he realizes the unknown women are chasing him.