The episode begins with Joey being upset with only getting a 20% tip. He needs to get new headshots taken and they are so expensive that he needs to make extra money in order to afford them. He decides to have some new medical experiments done on him to earn the money.
Later in the day Phoebe and Rachel return from a self defense and are convinced that they can kick anybody's ass. Ross is less convinced, saying that anybody can defend themselves from an attack they know is coming, but it's a whole other thing when it's a surprise attack. He tells them that you need to have something called "unagi." Rachel objects that unagi is a kind of sushi. Ross informs them that unagi is a state of total awareness. Chandler comes in and asks for help concerning what to get Monica for Valentine's Day. They had decided that they would make each other gifts, but he can't think of anything.
Later Chandler sits at home, trying to make a gift for Monica with little success. Monica comes home and he asks her if they really need to make the entire thing. She says that they do, and he leaves to go figure something out. Monica freaks out, having forgotten that they were supposed to make the gifts.
Joey goes to the hospital to partake in a medical experiment, but learns that they aren't looking for any applicants at the time, except for a study on identical twins.
Rachel and Phoebe come up to Monica and Chandler's apartment and are scared by Ross, who hid behind a wall and leaped out yelling "danger". He says it's a lesson in the importance of unagi, and wonders "at what point during those girlish screams would you have begun to kick my ass?" Monica exits to take out the trash and Ross yells "danger" after her but without getting a reaction. Ross concludes that Monica has unagi.
Meanwhile Joey goes to his audition and wonders where he could find a guy looking just like him to trick his way into the twin study. The room is filled with people looking like Joey.
Ross returns to his apartment and Rachel and Phoebe jump out from behind the curtains yelling "danger", causing Ross to scream out in a very girly fashion. Rachel concludes that Ross has "salmon skin roll".
Chandler searches his and Monica's bedroom to find something to give her, and discovers a mix tape. He goes out to Monica in the living room and gives her the tape, and she loves it. She asks him if "The Way You Look Tonight" is on it and he says they'll just have to listen and see. She gives her his gift, which turns out to be a sock bunny that Phoebe made. She confesses that she forgot that they were supposed to make the presents, and promises to cook him anything he wants and do anything he wants in bed. They rush into the bedroom.
Chandler is very content after their bedroom adventure, but Monica still feels she needs to do more to make it up to him. When they walk into the living room a strange guy comes in and greets them by name before getting a soda. He claims that he is Joey and tries to do Joey's "how you doin'?" However he does it wrong and Joey comes in, correcting him and sending him out in the hall. Joey tells Monica and Chandler that he hired Carl to be his identical twin.
Rachel and Phoebe come home and notice Ross' head sticking out from behind a chair. The scene cuts to Rachel and Phoebe having wrestled Ross to the ground and having him in a secure grip. Ross still refuses to acknowledge that they have unagi.
Joey and Carl go to the hospital to apply for the medical experiment. The doctor doesn't buy for a second that they are identical twins and Joey doesn't get to do the study.
Chandler comes home from work to find the apartment filled with candles and the table set for a romantic dinner. Monica wants to listen to the tape he made her while they have dinner, and puts it on. "The Way You Look Tonight" plays and she asks Chandler to dance with her. While they are dancing Janice's voice comes on the tape, revealing that she made it for Chandler on Valentine's Day. Monica is not happy.
Ross visits Rachel and Phoebe's self defense to get advice. He tells the instructor that he tried attacking his friend and his ex wife but it didn't work. Ross suggests that he and the instructor attack Phoebe and Rachel together, but realizes the instructor won't agree to that.
Meanwhile at Monica and Chandler's, Chandler is trying to apologize. Monica agrees to let it slide and celebrate Valentine's Day. They embrace and begin to dance again, but Janice's voice comes on the tape again, singing "My Funny Valentine". Monica goes into the bedroom and makes it clear that she does not want company.
Outside Central Perk Ross spots Phoebe and Rachel and moves to attack them. However Phoebe and Rachel are actually inside the coffee house. They see Ross sneaking by and attacking the two women he thinks are them. Ross begins to scream and runs by the coffee house, stopping when he notices Rachel and Phoebe, but then continues to run as the two other women chase him.