In the two-part episode, Chandler (Perry) runs into his grade school friend Susie (Roberts), working on the set of Outbreak 2: The Virus Takes Manhattan, a movie in which Ross’ (David Schwimmer) old pet monkey Marcel is appearing. Susie and Chandler end up going on a date, but he has no idea that her long game is to get revenge on him for humiliating her when they were kids when he pulled up her skirt during a school play. She convinces him to wear a pair of her underwear to the restaurant and then leaves him in a public bathroom stall after taking all the rest of his clothes. For a major mistake even big fans missed, check out The Embarrassing Friends Gaffe You Never Noticed Before. As it happens, Perry was key to securing Roberts as a guest star—and it involved some science. In The Hollywood Reporter’s oral history of the episode, co-creator Kevin Bright said Perry asked the Pretty Woman star to take the role.ae0fcc31ae342fd3a1346ebb1f342fcb “She wrote back to him, ‘Write me a paper on quantum physics and I’ll do it,’” Bright said. “My understanding is that Matthew went away and wrote a paper and faxed it to her the next day.” For more TV nostalgia sent right to your inbox, sign up for our daily newsletter. Whatever physics knowledge Perry displayed must have impressed Roberts. Because not only did she agree to play Susie, but from there, the casting negotiation also turned personal. “They may have met before the episode, but she was interested in him from afar because he’s so charming,” Friends staff writer Alexa Junge told The Hollywood Reporter. “There was a lot of flirting over faxing. She was giving him these questionnaires like, ‘Why should I go out with you?’ And everyone in the writers room helped him explain to her why. He could do pretty well without us, but there was no question we were on Team Matthew and trying to make it happen for him.” Neither Roberts nor Perry gave interviews for the oral history, so unfortunately, we may never know what exactly sealed the deal. For more star duos from this era, check out ’90s Celebrity Couples You Totally Forgot About. The fax flirting worked. The romance had run its course within the year, but Perry and Roberts did end up dating. It was the first A-lister relationship for the Friends star, and one that both actors have kept private, never speaking at length publicly about each other. Roberts went on to wed camera operator Danny Moder after meeting him on the set of The Mexican. They’ve been married for nearly 19 years. As for Perry, he got engaged to literary manager Molly Hurwitz last year. This particular ’90s celeb couple may not have been built to last, but hey: They’ll always have the fax machine in the Friends production office. And for more revelations about the classic sitcom, this was The Worst Friends Guest Star Ever, According to the Creators.