Axel Medellin has created this spot on mashup of the X-Men with the cast of The Big Bang Theory. I'm not sure about Penny's facial likeness here, but the rest seem spot on to me.
You'll probably need to look at the full size image to make out the text but I'd say the jokes were pretty much in character too. And the character mashups for the most part make sense to me, though Leonard as Wolverine probably over-states his coolness factor by several levels of magnitude.
Source: Deviantart - Axel Medellin