"The One With Phoebe's Dad" is the ninth episode of the second season of Friends, which aired on December 14, 1995.
It's Christmas time and Monica and Rachel are giving cookies as Christmas tips. The cookies, apparently, go down well only with Treeger. Ross is still trying to make peace with Rachel and buys her a Slinky, which she doesn't appreciate at all. He ends up giving the spring to Gunther. On Joey's insistence, Ross shows everyone his presents. Phoebe is stunned to find a picture of her father in Ross' photo frame, but she soon realizes it's a guy-in-the-frame picture and has suspects on her real father.
She asks her grandmother about her father and demands pictures of him, but all Grandma has are pictures of guys in frames. When Phoebe asks for the truth, she admits to her that she doesn't know anything about him - except for the fact that he's a pharmacist upstate and his home address. She also hands Phoebe a real picture of him. Phoebe takes Chandler and Joey with her for support, as the guys still have to do their Christmas shopping. At Monica's, Ross asks Rachel to make a list of cons he has to try and make her feel better, and then obsesses about them. When Monica asks him to turn off the heat, Ross breaks the knob off, causing the heat to leak. They end up having a Christmas summer party. As Rachel thinks he's incapable of seizing the day, Ross tips Treeger twice to try and get the radiator fixed, but Treeger explains how the store won't be open in time to fix anything.
Meanwhile, Phoebe tries to go knock at her father's door but can't, because she's worried that he might shut her off and she's not prepared to lose him like that. The amount of time she spends trying to go up to his house is such that Chandler and Joey don't manage to finish their shopping, but the guys support her decision and promise her that one day she'll be ready.
The guys and Phoebe make their way to Monica's apartment where the heat hits them - to everyone's surprise, Joey manages to turn off the heat by telling Monica that since the knob was broken, he turned the heat off from underneath. After, the group begins gift-giving, and Chandler and Joey start giving out theirs. Theirs are plainly the most bizarre Christmas gifts - Rachel gets wiper blades and a bottle of car smell; Phoebe gets toilet seat covers; Ross obtains a cola drink and a lemon-lime; whilst Monica receives a packet of ribbed condoms. Ross and Monica gladly exchange their gifts.