Season 2 - 23. The One With The Chicken Pox

Phoebe catches chicken pox just as her old flame Ryan arrives in town on leave from the Navy. Even though he hasn't yet had chicken pox, he can't stand to be apart and they both spend the rest of the time trying to not scratch. Joey gets a job at Chandler's office but decides to play it as a role. The character he creates, Joseph, has a wife and kids and ultimately blames Chandler for his own screwup. Monica is upset that Richard doesn't have a "thing": an unexplainable quirk. He eventually comes up with one to ease her mind.