"The Big Bang Theory" Season 10 aired its twelfth episode titled "The Holiday Summation" this week. The episode was riddled with flashbacks about how the gang celebrated their respective holidays. Sheldon (Jim Parsons) and Amy (Mayim Bialik), for instance, went to Texas to visit the former's mother and got another relationship milestone in the process.

While they are on the road, Amy convinces Sheldon that they reveal their cohabitation to Mary Cooper (Laurie Metcalf). Sheldon initially refused because he believes that his mother would only impart some silly Christian lecture on them.

Much to Sheldon's surprise, Mary was thrilled with the idea and even told her son that, "By your third birthday, you had memorized over a thousand different kinds of trains. And I never imagined a woman getting aboard any of them," according to Vulture. Sheldon took this the wrong way and felt bad that his mother still sees him as this weirdo who's incapable of settling down and getting tied to a relationship.

Sheldon proceeds to mock his mother's view of him and wears underwear on his head and a pair of swim fins on his feet. Amy, always the sweet and understanding one, takes Sheldon to a drive and tells him that what he should focus on is that his mother was proven wrong in her expectations of him.

Amy also reveals that she informed Mary of their living arrangement even before they landed in Texas. That's the reason why Mary instantly warmed up to the couple's living arrangement. Amy also says she did it to help Sheldon's shortcomings, and "The Bang Theory" fans know how difficult he can be in almost every emotional circumstance.

Leonard (Johnny Galecki) and Penny (Kaley Cuoco), meanwhile, had a fight over the latter watching episodes of "Luke Cage" in advance instead of waiting for her beau. However, the real reason for their fight was Leonard mishandling the chopping down of their Christmas tree.

Just taking a break. #BigBangTheory pic.twitter.com/dUMywPS53e

— The Big Bang Theory (@bigbangtheory) January 6, 2017

Bernadette (Melissa Rauch) and Howard are having a hard time with their baby daughter Halley. The infant won't stop crying unless Stuart's (Kevin Sussman) voice is soothing her. This made Bernadette doubt her parenting, but she found that snuggling with the baby until she falls asleep is effective in calming her down.

Episode 12 of "The Big Bang Theory" didn't reveal Raj's (Kunal Nayyar) holiday whereabouts. Stu paid his grandmother a visit in Bakersfield.

It appears that there is no new "The Big Bang Theory" episode next week, CarterMatt reported. The next episode will likely arrive on CBS on Thursday, Jan. 19. What do you think of the latest "The Big Bang Theory" episode? Share your thoughts below!