That character is from the initially-unaired pilot ("The Cage"), but that shot (and actor) is from "The Menagerie" - a 2-part episode from the first season that re-used scenes from The Cage as flashbacks.

They had Pike injured and in the wheelchair so they could use makeup and the "beep" communications to disguise the fact that the actor playing him was different in the newly-filmed scenes versus those from the flashbacks.