My Straight, Physicist, More Socially Ill-Adjusted Alter-Ego

With thanks to Battochio for the title of this posting, he was the second person I know who has pointed out that the guy on The Big Bang Theory (Jim Parsons, who plays Sheldon) reminds them of me. I have only watched snippets of the show, and apart from his build, his hair colour, hairline, his tendency to wear longsleeved t-shirts under short sleeved ones, and his brilliance, I don't really see a resemblance. Thoughts?