In the next episode of the "The Big Bang Theory," Sheldon (Jim Parsons) gets some unlikely help from Penny (Kaley Cuoco) regarding his research.

The trailers and promotional pictures for the upcoming installment, which is titled "The Solo Oscillation," were just released recently, and they show Penny going over to Sheldon's apartment and knocking on the door.

"Sheldon, Sheldon, Sheldon," she says as she knocks three times on the door. The physicist opens it and says to Penny seriously, "It's annoying when you do it."

She brushes that aside and enters the premises with pizza. Sheldon then informs her that he has been having a difficult time coming up with an alternate approach to his research on dark matter. Penny listens and appears to be willing to help him.

Apparently, Sheldon left his work on "String Theory" and is now focusing on dark matter. "So it's your rebound science," Penny asks the scientist who seems to be confused. "What's that?" he says to her.

She replies authoritatively, "Well, it's not the science you want to spend the rest of your life with, but it's the one you use to make yourself pretty again." Sheldon realizes that she makes some sense, and he decides to listen to her advice. It remains to be seen if Penny will be able to help the genius come up with an approach to dark matter.

In the last episode, Amy (Mayim Bialik) decided to pick Penny as her maid-of-honor at her upcoming wedding. At first, she was going to ask Bernadette (Melissa Rauch) to be the one, but Penny somewhat forced Amy to pick her because they were best friends. Amy was glad about her decision in the end.

"The Big Bang Theory" season 11 episode 13 will hit the airwaves on Thursday, Jan. 11, at 8 p.m. EST on CBS.