Rosie O'Donnell joins ET's countdown continues to the premiere of The CW's new "90210" spin-off with a cameo role in this Web exclusive clip from the original "Beverly Hills, 90210."

Rosie plays herself in the "Destiny Rides Again" episode from season three when she appears as the host of an AIDS benefit attended by the West Beverly High gang. In this scene, she confronts Brandon (Jason Priestly), who admits he has had sex, and compliments Donna (Tori Spelling), who reveals she is a virgin.

Before the launch of the new series, SOAPnet will celebrate the original Aaron Spelling show with a 24-hour marathon, starting at midnight on Monday, Sept. 1 -- with ETonline giving you a sneak peek of the episodes that will air!

Then, on Tuesday, Sept. 2 at 8 p.m., the all-new "90210," starring Rob Estes, Lori Loughlin, Shenae Grimes, Tristan Wilds and Jennie Garth will premiere with a special two-hour episode on The CW when the Wilson family moves to Beverly Hills.