'The Big Bang Theory' Season 5 pictures: Raj & Penny's tryst and Sheldon being Sheldon

Even squares can have a love triangle.

The CBS comedy "The Big Bang Theory" had quite the cliffhanger to close out Season 4. Raj (Kunal Nayyar), who is essentially a mute around women unless he has a couple cocktails, had his own "Big Bang" with Penny (Kaley Cuoco) after a night of drunken commiseration.

Raj and Penny's night together will no doubt cause a bit of confusion among the gang of geniuses, especially Leonard (Johnny Galecki), who dated Penny earlier in the series. We'll also learn how serious Priya (Aarti Mann) is about breaking up with Leonard and moving back to India. Plus it's clear Leonard still has feelings for Penny.

The season premiere will also have Sheldon (Jim Parsons), Howard (Simon Helberg), Leonard and Raj taking part in a paintball competition. It's no surprise that Sheldon will be commanding the troops as he's done so many times before.

The only other question remaining is how will Howard cope with Bernadette's (Melissa Rauch) professional and financial success. We're guessing poorly.

"The Big Bang Theory" begins its fifth season on Sept. 22 at 8 p.m. ET.

Here are some production stills from the season premiere.