Friends was a show in some ways like the show Seinfeld. It was another sitcom about a bunch of friends living in New York. Unlike most Seinfeld clones though, Friends managed to establish an identity of its own and become a success in its own right.

At the time it started, one of its stars, Lisa Kudrow who played Phoebe Buffay, was also appearing in a recurring role on the sitcom Mad About You as Ursula. Ursula was an incompetent waitress at a restaurant frequented by the shows main characters Paul and Jamie. It wouldn't be impossible for Lisa to do both shows since Ursula was not a central character and just appeared occasionally. But the conflict did get people behind the scenes thinking. Both shows were set in New York. Both shows were on NBC. Maybe they could do something with this situation. So they did.

It was soon revealed that Phoebe and Ursula were estranged twin sisters. The character of Ursula made a number of appearances on Friends. At one point she was dating Phoebe's friend Joey. Phoebe was concerned for Joey knowing that Ursula was a flake and would break his heart. And she did. Ursula stopped seeing Joey without even telling him she was dumping him. Phoebe stepped in pretending to be Ursula and broke up with Joey properly even giving him a goodbye kiss. Joey quickly realized it was Phoebe and was touched by her trying to do such a sweet thing.

Phoebe and Ursula's mom had committed suicide when they were both very young. In another episode Phoebe discovered that the woman they had considered their mother was not in fact their real mother. Even though she hated Ursula she felt she had to tell her this important news. When she told Ursula, Ursula told her she already knew. How? "Oh, it was in the suicide note," Ursula explained matter of factly. Phoebe was stunned. There was a note? She didn't know there was a note! Phoebe asked Ursula if she still had it and if she could see it. Somewhat annoyed Ursula went off and returned with a note that said something along the lines of "Goodbye cruel world. Your real mom lives at X location" and that was clearly something Ursula had just written (having long pitched the real suicide note. Nice.

In yet another episode of Friends, a couple of other major Mad About You cast members put in an appearence. One of the main locations for Friends was a coffee house the friends frequented named Central Perk. In the episode in question, Mad About You's Jamie and her friend Fran stopped in to Central Perk. They saw Phoebe and started wondering if she was Ursula, their waitress from the restaurant on Mad About You. They approached her and started talking to her as if she was Ursula. Phoebe, not picking up on that they were confusing her for her sister, answered their questions with more than a little confusion which, to them, made her sound like an utter airhead. That convinced them for sure that she was Ursula.