When “Grey’s Anatomy” introduces Dr. Lauren Riley in its Feb. 13 episode, “Save the Last Dance for Me,” it marks more than just Shoshannah Stern’s debut on the long-running drama: Dr. Riley is also the first recurring deaf doctor on a primetime network series.

To tackle the groundbreaking character, Stern teamed up with “Grey’s Anatomy” showrunner Krista Vernoff, who initially didn’t realize this would be a historic first.

“I didn’t know until we were on set shooting it,” Vernoff tells Variety, calling the vibe on set “electric.” “And that is the power of Shoshannah: I fell in love with her as a human, as a communicator, as an actress. I thought she was incredible and I wanted to put her on my show. I did not even know it had never been done before. That’s wild to me. And so to learn that on the day that...