Gallagher joins the Grey's cast in very attention-grabbing fashion as Dr. David Hamilton, a Minnesota-based doctor who convinces Meredith to work on a Parkinson's research project that he has a very personal connection with. According to Deadline, he's set to recur throughout the season, and it may not just have to do with the Parkinson's project. In his first appearance, he casually comments to Meredith that he knew her mother, Ellis Grey, back in the day.
Gallagher's résumé is full of recognisable roles and buzzy projects. Millennials probably best remember him from The O.C., and his more recent major gigs include roles on Grace and Frankie and Zoey's Extraordinary Playlist.