The Big Bang Theory came back from a two-week hiatus with one of its strongest episodes of season 6, featuring more than one surprising – and touching – moment for the ordinarily distant Dr. Cooper.

In “The Cooper/Kripke Inversion,” Sheldon is disdainfully dismayed to learn that he and fellow physicist (and frequent nemesis) Barry Kripke must work together on a grant proposal for the university. But Sheldon’s irritation becomes despair when he realizes that Kripke’s research far surpasses his own. Sheldon is reduced to such a fragile state that he accepts Amy’s offer of a hug.

But to Sheldon’s surprise, Kripke chalks up Sheldon’s mathematical missteps to all of sexytimes he – supposedly – shares with Amy. Sheldon rolls with the interpretation in the face of Kripke’s admiration, and his inexperienced assertions fly right over the envious lisper’s head.

Sheldon bemusedly relates all of this to Leonard and Penny, at which point Penny tosses aside all restraint and asks the question which has clearly been burning in the back of her mind for years: Is Sheldon ever going to get physical with Amy? Sheldon’s careful answer: “It’s a possibility.”

Remember this moment, Big Bang fans. It’s one for the history books. (Or maybe the science books?)

Elsewhere in Pasadena, Howard and Raj order expensive custom-made action figures of themselves. When the results are disappointing, they purchase an even more expensive 3D printer. But Howard gets in hot water with Bernadette over his frivolous use of her money and is forced to sell his new plastic baby to Raj.

The Big Bang Theory will be back next week with “The Spoiler Alert Segmentation.” CBS says:

When Sheldon and Leonard fight, it affects Penny and Amy’s living arrangements. Meanwhile, Raj takes care of Mrs. Wolowitz while Howard is away.

And “The Tangible Affection Proof” will air on Feb. 14. (Three guesses what the theme will be!)

While the guys try to give their significant others the perfect Valentine’s Day, Raj and Stuart throw a “lonely people” party at the comic book store.

What did you think of ‘The Cooper/Kripke Inversion’?