The initial two-hour episode of Greys Anatomy, which is expected to start the spin-off series and is titled "The Other Side of This Life" (Parts I & II), has just finished filming, according to Diggs.
"We're hoping people dig it," Diggs said.
ABC plans to test out the show with a "back-door pilot," an expanded two-hour episode of Grey's Anatomy, USA Today reported in February.
The air date for the episode has not been set by ABC, officially, although sources tell us it will be May 3.
"Plot what? Secrets?" he said. "I can't tell you! It's a secret."
Grey's Anatomy creator and executive producer Shonda Rhimes is writing the first episode, which, according to several accounts, will feature Dr. Addison Montgomery (Kate Walsh), mulling an out-of-town job offer.