HALLOWEEN IS FULL OF SURPRISES FOR THE SEATTLE GRACE DOCTORS WHEN AVA MAKES AN UNEXPECTED VISIT TO SEE ALEX, MEREDITH THINKS HER DECEASED MOTHER IS HAUNTING HER, AND CALLIE REVEALS GEORGE AND IZZIE'S AFFAIR TO THEIR FELLOW DOCTORS, ON ABC'S "GREY'S ANATOMY"

Elizabeth Reaser Reprises Her Emmy-Nominated Performance as Ava

Edward Hermann ("Gilmore Girls") Returns as Dr. Norman Shales

"Haunt You Every Day" � It's Halloween, and the day is full of surprises for the doctors of Seattle Grace � Alex receives an unexpected and welcome visit from his former patient, Ava/Rebecca, Meredith is convinced that her mother's ashes are haunting her, Cristina is snubbed by a surgeon she admires, and Callie announces George and Izzie's affair to their fellow doctors, on "Grey's Anatomy," THURSDAY, OCTOBER 25 (9:00-10:02 p.m., ET) on the ABC Television Network.

"Grey's Anatomy" stars Ellen Pompeo as Meredith Grey, Patrick Dempsey as Derek Shepherd, Sandra Oh as Cristina Yang, Katherine Heigl as Isobel "Izzie" Stevens, Justin Chambers as Alex Karev, T.R. Knight as George O'Malley, Chandra Wilson as Miranda Bailey, James Pickens, Jr. as Richard Webber, Sara Ramirez as Callie Torres, Eric Dane as Mark Sloan and Chyler Leigh as Lexie Grey.

Guest Cast: Edward Herrmann as Norman, Elizabeth Reaser as Ava, Rocky Carroll as James, Kali Rocha as Sydney, David Clennon as Jack, Dylan Minnette as Ryan, Sarah Utterback as Olivia and Anjul Nigam as Raj.

"Haunt You Every Day" was written by Krista Vernoff and directed by Bethany Rooney.

"Grey's Anatomy" is broadcast in 720 Progressive (720P), ABC's selected HDTV format, with 5.1-channel surround sound and Spanish audio via SAP. This program carries a TV-14,S parental guideline.

This episode of "Grey's Anatomy" will be available on ABC.com the day after airing on the network for users to watch online.