A CHANCE REUNION IN THE E.R. BETWEEN TWO LONG LOST LOVERS MAKES EVERYONE REASSESS THEIR PERSONAL LIVES, ON ABC'S "GREY'S ANATOMY"

Demi Lovato ("Sonny with a Chance," "Camp Rock") Guest Stars as Hayley, and Marion Ross ("Happy Days") Guests as Betty

"Shiny Happy People" - An elderly patient admitted into the E.R. for a heart condition sees a familiar face, a long lost love who happens to be in the E.R. as well for a fractured arm, and the staff find themselves caught up in their love story. Meanwhile, Karev treats a troubled teenage patient (guest star Demi Lovato) whose parents brought her in for schizophrenia, and Meredith can't help but tell Cristina about her suspicions of Owen -- which inevitably messes with Cristina's head -- on "Grey's Anatomy," THURSDAY, MAY 13 (9:00-10:01 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, Justin Chambers as Alex Karev, Chandra Wilson as Miranda Bailey, James Pickens, Jr. as Richard Webber, Sara Ramirez as Callie Torres, Eric Dane as Mark Sloan, Chyler Leigh as Lexie Grey, Kevin McKidd as Owen Hunt and Jessica Capshaw as Arizona Robbins.

Guest cast include Jesse Williams as Jackson, Nora Zehetner as Reed, Jason George as Ben, Demi Lovato as Hayley, Marion Ross as Betty, Allan Mandell as Henry, Amy Farrington as Mary, Jonathan Goldstein as Ken, Austin Highsmith as Amber and Emily Bergl as Trisha.

"Shiny Happy People" was written by Zoanne Clack and Peter Nowalk and directed by Ed Ornelas.

"Grey's Anatomy" is broadcast in 720 Progressive (720P), ABC's selected HDTV format, with 5.1-channel surround sound. A TV parental guideline will be assigned closer to airdate.

For more information on "Grey's Anatomy," visit ABC.com.