Summer Glau on The Big Bang Theory

It's pure nerd-vana on the March 9 episode of CBS' The Big Bang Theory when Summer Glau — butt-kicking Cameron on Fox's Terminator: The Sarah Connor Chronicles — guest-stars as herself. And this photo is a first look at what is ostensibly the gang's reaction to stumbling upon (perhaps literally) the sci-fi siren.

How do Leonard, Sheldon et al come to be within sniffing distance of the brunette beauty? The unlikely, would-be encounter comes to pass as the boys trek to a sci-fi convention, only to realize that one of its biggest draws is riding the same train as them.

Also appearing in the sweeps episode — and giving TV's "fourth wall" an equally fun nudge — is Nobel Laureate Dr. George Smoot, aka the father of the Big Bang Theory of Creation. But in all fairness, his abs don't look as good as Summer's.