Speedman only appeared in one episode in season 14 as Nick, a transplant surgeon who bonds with Meredith when he needs emergency surgery for a transplant complication of his own. But his chemistry with Meredith was enough to convince the Grey's team to bring him back four whole seasons later! He's now a series regular in season 18.
Of course, Speedman has a pretty recognisable résumé even outside of Grey's! He's best known as one of the leads on the WB drama Felicity, for his regular role on Animal Kingdom, and, more recently, for You. With Meredith spending time doing research in Minnesota, where Nick works, it looks like their years-ago spark might reignite!