Sheldon (Jim Parsons) and Amy (Mayim Bialik) are set to have sex in an upcoming episode of “The Big Bang Theory” Season 9. Parsons has said that he was surprised when he came to know about the next milestone in Sheldon and Amy’s relationship.

“I was very surprised,” Parsons said to ET. "But then I read it, and it seemed absolutely the right time." Bialik said that she too was surprised to learn that Amy and Sheldon are finally going to have sex.

They are “putting the 'bang' into the theory, I guess," Parsons said.

ET’s video footage reveals that Sheldon is set to lose his virginity on Amy’s birthday, and the video also features their passionate kiss. Parsons said that it was fun to act, while Bialik added that the filming of the scene was not “icky” but “tender.”

Earlier in November, executive producer Steve Molaro said in a statement that it was the right time for Sheldon and Amy, who broke up in Season 8 finale of “The Big Bang Theory,” to take their relationship to the next level. “After over five years of dating, we felt the time was right for Sheldon and Amy to finally consummate their relationship, and we're so excited for the audience to see the journey over the next several episodes," he said.

Sheldon and Amy first met in the final episode of “The Big Bang Theory” Season 3 thanks to Raj (Kunal Nayyar) and Howard (Simon Helberg) putting Sheldon's profile on an online dating site. Their relationship has been anything but smooth, and they have taken their own sweet time to kiss each other and confess their love for each other.

Meanwhile, ET’s footage also provides a glimpse of Professor Proton (Bob Newhart). The report revealed that his apparition will be making an appearance to help Sheldon make an important decision of his life. Professor Proton passed away in Episode 22 of “The Big Bang Theory” Season 7, titled “The Proton Transmogrification."

Sheldon and Amy are going to consummate their relationship in the episode that is scheduled to air on Thursday, Dec. 17, on CBS in the U.S.

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