Though it is yet unclear what character Morrison is playing, he revealed a major clue in his Instagram story, reported Entertainment Tonight.
"I'm back to filming. I can't say what I'm on yet, but my name is Dr Paul Stadler," Morrison said dressed in a tie and suit with his hair slicked back.
A "Grey's Anatomy" fan site also shared a video and an on-set photo of Morrison with Justin Chambers, who plays Alex Karev in the show.