Practice makes perfect, the old saying goes -- and Alyson Hannigan said Thursday she's been improving her fake orgasms "all the time" as she prepares for the new London stage adaptation of "When Harry Met Sally ..." costarring Luke Perry, PEOPLE reports.

For those who might have forgotten, leading lady Meg Ryan famously faked a loud orgasm in a New York deli in the 1989 movie, which costarred Billy Crystal.

But that was then. Now Hannigan, 29, best known for her roles in "Buffy the Vampire Slayer" and the "American Pie" films, will reinterpret the role of Sally for the West End stage when it debuts Feb. 20.

She and Perry, 38, who'll play Harry (and is probably best remembered as the brooding Dylan McKay on TV's "Beverly Hills, 90210"), have been rehearsing in London since Monday and are excited about the potential for the play.

Perry said he "couldn't pass it up" when asked to join the cast, while Hannigan (recently married to "Angel" star Alexis Denisof, 36) believed that the show was important enough to justify the separation from her new hubby. Still, she did insist, "We've got every technology out there to stay in touch."

"When Harry Met Sally ...," based on the Nora Ephron screenplay, will open at the Theatre Royal Haymarket and feature music by two of the U.K.'s hottest new jazz stars, Jamie and Ben Cullum. (Jamie's album, "Twenty Something" is the fastest-selling jazz recording in British history.) The two have reworked the original movie score, adding a few compositions of their own.

As for that memorable bit of moaning, head-shaking and table slapping that Sally does so well, Hannigan assures (with a laugh): "Well, Meg Ryan and I are different people, so I'm sure our orgasms will be slightly different."