darquegk said: "I think it’s not so much that he’s “playing Sheldon.” It’s more that after two or three seasons, Parsons and the Big Bang Theory turned down his “severe, austere autistic robot” portrayal from the show’s initial run. Instead, Parsons gradually substituted more and more of his own eccentric affect, which is the point when Sheldon became a beloved character, not just an ensemble player.
”Fey Jimmy Stewart from outer space” is just who Parsons IS, or at least defaults to when in performance mode. He did an interview on Conan or Jimmy Fallon about his early days in theatre, where he got cast in a role written to be played with a South African affect, simply because his affect was unusual enough that they took him anyway."
Point taken, but it still means he plays every role (with the exception of the early seasons Sheldon) exactly the same way. And to me, it's boring.