This is a photo from "The Itchy Brain Simulation." It's Episode 7 of The Big Bang Theory Season 8.
Sheldon makes Leonard pays for a past mistake on The Big Bang Theory. "The Itchy Brain Simulation" is the eighth episode of the show's seventh season.

The Big Bang Theory Season 7 Episode 8 Quotes

Leonard: How about that? Sheldon's being reasonable.
Penny: Yeah, it's freaking me out. I'm gonna go.

Leonard: I'm gonna show you what's in the box, but just ... promise not to flip out.
Sheldon: Why would I flip out? Is it a spider? It's a spider.
Penny: No, if it was a spider, Lenny would've flipped out.