The Vengeance Formulation (2009)

Barry Kripke severely embarrasses Sheldon on National Public Radio's talk show "Science Friday" by filling Sheldon's office with helium so that his voice is higher pitched than usual. While at first pouting and announcing defeat, Leonard and Raj , convince Sheldon to fight back. Sheldon takes vengeance on Kripke with an elaborate trap in which a massive cloud of gooey foam, to be set off by a human presence in Kripke's office, falls through the ceiling into Kripke's office, effectively covering him in foam. However, the trick backfires on him when the visiting Caltech president and board of directors are also hit, thanks to Sheldon's lack of an "abort" system. Sheldon gives himself away with a pre-recorded video stating that he sent the taped trick to YouTube, and proclaiming himself the mastermind. Leonard and Raj also share the consequences when Sheldon gives them their share of the credit.

Meanwhile, Howard's new girlfriend, Bernadette, asks him where their relationship is going after their third date. He avoids her for a week, thinking about whether he should "settle" for her or hold out for the impossible . After a dream in his tub involving a romantic evening turned lecture from Katee Sackhoff, he decides that he should stick with reality. He proposes to Bernadette at the Cheesecake Factory, gets rejected, and then sings her his version of the song "Bernadette" in order to win back her affections, in which he becomes successful when she declares it as the most romantic thing anyone has ever done for her.

Recurring characters: Melissa Rauch as Bernadette Rostenkowski and John Ross Bowie as Barry Kripke

Title reference: Sheldon's revenge against Kripke.