It's time to see who'll be Head Geek in the event of superpowers being dished out...

"The Alien Parasite Hypothesis"

Poor Sheldon and Amy. Not even the Vulcan discipline of Kolinahr can keep sex from rearing its ugly head in their lives eventually. And here we're talking about a couple ("We're not a couple!") whose connection to their inner needs and feelings is as distant as Voyager 1 (which, at its current location of 116 million miles from Earth, is pretty damned distant).

When Amy finds herself having a touch of the vapors after being introduced to Zack (Thomas Smith), another of Penny's numerous sexual cast-offs, it takes a long session of scientific analysis with not-boyfriend ("Really! He's not my boyfriend!") Sheldon to work out that she might be in the throes of lust for the first time in her life. Either that or she's being possessed by an alien parasite - and that's where Sheldon's smart money is.

But Dr. Cooper is wrong, and - during a long and pleasantly oblivious walk through his own jealousy in the borough of Denial - hilariously sets about finding Zack's phone number by contacting every Zack Johnson in the phone book to ask if he's the 'Zack who had coitus with Penny'. Eventually he manages to set up a date between the two - but when faced with the prospect of sexual congress with a man-ape whose cranial cavity is full of Final Frontier, Amy finally takes her first step to understanding the concept of 'slumming it', and turns wisely to Sheldon's recommendations that Kolinahr's self-denial is a better option than getting entangled in carnal matters.

Over in the side-story, Raj's disappointment in finding that a radioactive rat-bite has not turned one of the gang's colleagues into a feral superhero leads to a theoretical game of wits between himself and Howard as to which of them would end up as 'the sidekick' if both had superpowers. Howard tests Raj's arachnophobia in a bid for an early win, only to end up squealing as a tarantula goes for a walk on his own jumper. Ultimately the matter is proposed to be settled with a prolonged wrestling session at the local gym - if either of these two ever gets past the superhero banter long enough to go for a move. Or actually make physical contact of any type...

It took six people to write this episode (Chuck Lorre, Steven Molaro, Steve Holland, Lee Aronsohn, Jim Reynolds and Maria Ferrari) and it shows - Alien Parasite Hypothesis is a tag-teamed tirade of comedy quips and amusing moves; not only does the geek comedy never let up, but the Sheldon/Amy dynamic is nudged forward by exactly as much as is needed without taking over the episode or sacrificing the humor.

Jim Parsons and Mayim Bialik are arguably the best 'social inadequates' on TV since Lt. Data puzzled the ways of humanity in Star Trek: The Next Generation; and even when he's sidelined, Leonard (Johnny Galecki) manages equal comedic impact as the geek-nearest-to-normal in this crowd of Star Trek-obsessed nuts.

Meantime Kunal Nayyar is really having a development boost in season four; truth is, he did used to be Simon Helberg's sidekick on The Big Bang Theory, and I wonder if it's a coincidence that his noticeable extra input into the show's comedy quotient in season four coincides with the stand-off between Raj and Howard (or is that Howard and Raj) this week..?

This show just won't drop its guard this season, and Alien Parasite proves yet another comedy sucker-punch for The Big Bang Theory.

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