Title: Addison Montgomery
Content:  Addison Adrianne Forbes Montgomery, M.D., F.A.C.S., F.A.C.O.G  is a fictional character on the ABC television series Grey's Anatomy and Private Practice played by Kate Walsh. Addison is a world-class neonatal surgeon with board certifications in both Obstetrics and Gynaecology and Maternal and Fetal Medicine. Additionally, she has completed a medical genetics fellowship. She works at the Oceanside Wellness Group, a fictional practice located in Santa Monica, California. Addison joined the series in the first-season finale as Derek Shepherd (Patrick Dempsey)'s estranged wife. Initially set for a recurring guest stint on Grey's, Walsh's character expanded into a series regular position as Rhimes grew fond of Walsh's portrayal of the character. She is promoted to series regular in season two episode seven, "Something To Talk About". She makes her final appearance as a series regular in the season three finale, "Didn't We 
Title: Grey's Anatomy (season 2)
Content:  surgeon Preston Burke, who learns that Cristina, with whom he had a sexual relationship, is pregnant with his child. Patrick Dempsey portrayed attending neurosurgeon Derek Shepherd, whose relationship with intern Meredith Grey has been the focal point of the series since its inception. Although originally conceived as a guest-star with a 5-episode story arc, Kate Walsh decided to extend her contract following positive reviews from critics and fans, resulting in her getting promoted to series-regular status. Being the first addition to the original cast from the first season, Walsh began receiving star-billing in the seventh episode of the season, portraying obstetrician-gynaecologist and world-class neonatal surgeon Addison Montgomery Shepherd, who comes in Seattle seeking reconciliation 
Title: Grey's Anatomy (season 15)
Content:  the first gay male surgeon to appear on the show. On October 10, 2018, it was announced that Josh Radnor had been cast as Meredith's new love-interest. On December 13, 2018, it was announced that Jennifer Grey had been cast in "a mysterious role," later to be revealed she portrayed Brittany's mom. It was announced on February 13, 2019, that Amy Acker had been cast as Derek Shepherd's fourth sister, Dr. Kathleen Shepherd. Acker is expected to appear in 1 episode this season, that episode being an Amelia-centric episode. On March 5, 2019, it was revealed that Abigail Spencer would reprise her role as Megan Hunt for 1 episode this season, which will air during spring.
Title: Grey's Anatomy (season 5)
Content: Kate Walsh as Addison Montgomery ; Tyne Daly as Carolyn Maloney Shepherd ; Loretta Devine as Adele Webber ; Héctor Elizondo as Carlos Torres ; Bernadette Peters as Sarabeth Breyers ; Faye Dunaway as Margaret Campbell ; Debra Mooney as Evelyn Hunt ; Sharon Lawrence as Robbie Stevens ; Perrey Reeves as Margaret ; Mark Saul as Dr. Steve Mostow ; Brandon Scott as Dr. Ryan Spalding ; Steven W. Bailey as Joe, the Bartender ; Lauren Stamile as Nurse Rose ; Leslie Grossman as Lauren Hammer ; Liza Weil as Alison Clark ; Leslie Odom, Jr. as P.J. Walling ; Nicole Cummins as Paramedic Nicole ; Audra McDonald as Naomi Bennett ; Taye Diggs as Sam Bennett ; Grant Show as Archer Montgomery 
Title: Kate Walsh (actress)
Content:  with Conan O'Brien. Walsh had a recurring role on Karen Sisco as Detective Marley Novak in 2003 and 2004. In 2005, she was cast in her breakout role in the ABC series Grey's Anatomy, as Dr. Addison Montgomery, the estranged spouse of Derek Shepherd ("Dr. McDreamy", played by Patrick Dempsey). In February 2007, Walsh's Grey's Anatomy character received a spin-off of Grey's Anatomy that began airing in September 2007. Taye Diggs, Tim Daly, Amy Brenneman, Chris Lowell, and Audra McDonald were cast in the spin-off, Private Practice. Walsh would return for six episodes across the fourth through eighth seasons of Grey's Anatomy, including the musical episode "Song Beneath the Song". On 
Title: Grey's Anatomy (season 6)
Content: Kate Walsh as Dr. Addison Montgomery ; Sarah Drew as Dr. April Kepner ; Jesse Williams as Dr. Jackson Avery ; Jason George as Dr. Ben Warren ; Nora Zehetner as Dr. Reed Adamson ; Robert Baker as Dr. Charles Percy ; Leven Rambin as Sloan Riley ; Jeff Perry as Thatcher Grey 
Title: Derek Shepherd
Content:  Derek Christopher Shepherd, M.D., F.A.C.S., also referred to as "McDreamy", is a fictional surgeon from the ABC medical drama Grey's Anatomy, portrayed by actor Patrick Dempsey. He made his first appearance in the pilot episode, "A Hard Day's Night", which was broadcast on March 27, 2005. Derek was married to Addison Montgomery (Kate Walsh) before their divorce in 2007. Before his death in 2015, Derek was happily married to his longtime partner and wife Meredith Grey (Ellen Pompeo). The couple had three children together. Shepherd was formerly the Chief of Surgery at Seattle Grace Mercy West (now Grey Sloan Memorial Hospital) but abruptly resigned from his position as Chief in season 7 following the shooting. Dempsey was nominated for the 2006 and 2007 Golden Globe for Best Performance by an Actor in a Television Series Drama for the role, and the 2006 SAG Award for Outstanding Performance by an Actor in a Drama Series.
Title: Addison (given name)
Content: Addison Montgomery, a character on the television series Grey's Anatomy 
Title: Grey's Anatomy (season 15)
Content: Okieriete Onaodowan as Dean Miller ; Jasmine Guy as Gemma ; Debra Mooney as Evelyn Hunt ; Josh Radnor as John ; Jeff Perry as Thatcher Grey ; Michelle Forbes as Vicki Ann Rudin ; Michael Evans Behling as Brady ; Abigail Spencer as Dr. Megan Hunt ; Tyne Daly as Carolyn Shepherd ; Amy Acker as Dr. Kathleen Shepherd ; Embeth Davidtz as Dr. Nancy Shepherd ; Khalilah Joi as Abby Redding ; Joshua Bassett as Linus ; Boris Kodjoe as Robert Sullivan ; Brett Tucker as Lucas Ripley 
Title: Grey's Anatomy (season 4)
Content:  • Kate Walsh as Dr. Addison Montgomery • Mark Pellegrino as Chris • Caroline Aaron as Connie • Michael McGrady as Stanley Singer • Miriam Flynn as Gretchen Bitzer • Amy Hill as Joanne • Dylan Minnette as Ryan • Matt Lanter as Adam Singer • David Clennon as Jack Shandley • Kurt Fuller as Jerry • Seth Green as Nick Hanscom • Gale Harold as Paramedic Shane • John Billingsley as Jacob Nolston • Alison LaPlaca as Mrs. Nolston • Kimberly Huie as Mary Daltrey • Nicole Cummins as Paramedic Nicole • Theo Rossi as Stan Giamatti • Cheech Marin as Otis Sharon • Paul Dooley as Dr. Walter Tapley • John Cothran as Ken Monroe • Kathryn Meisle as Liz Monroe • Jurnee Smollett as Beth Monroe • Jana Kramer as Lola • Sterling Knight as Kip

Question: who plays addison shepherd on grey's anatomy?
Answer: Kathleen Erin Walsh.