Sheldon defines the word cool when he puts on his toy hulk hands and in front of Raj.
After meeting two girls at the university mixer, Raj and Sheldon invite them for a raging game of Rock Band at the apartment.
Sheldon helps decorate the tree and wants to add the bust of Sir Isaac Newton, which he argues is more Christmasy than Jesus.
After years of trying to get his mother's affection, Leonard finally gets a hug from Beverly (Christine Baranski). All it took was getting her drunk.
Penny and Leonard's mom, Beverly (Christine Baranski) go for some shots of tequila at the Cheesecake Factory.
Holy kissy face! That's Leonard's mom kissing Sheldon in this stunning photograph.
Penny comes to Sheldon for help to better understand Leonard's work and here he is training her.
Bernadette (Melissa Rauch) joins the guys for lunch at work as she begins to bond with Leonard over his work.

TBBT Quotes

Penny: Here's a question-- as an alien pretending to be human, are you planning to engage in any post-prom mating rituals with Amy?
Sheldon: There are post-prom mating rituals?
Penny: Not always. Unless your date drives a van with an air mattress, then always.
Sheldon: Well, if it's part of the prom experience, then I'm open to it.
Penny: You're kidding.
Sheldon: I may be an alien, but I have urges.If Amy wants to copulate by firing her eggs into space, well, then, I will happily catch them with the reproductive sac on my upper flermin. I'm not the best at reading facial cues, but I can see that you're a little turned on.

Raj: Well, to paraphrase Shakespeare: It's better to have loved and lost than to stay home every night and download increasingly shameful pornography.
Penny: Oh... you poor baby.
Raj: What's wrong with me, Penny?
Penny: Nothing, nothing. You know, if we weren't friends - and you hadn't brought up that creepy pornography story - I'd be on you like the speed of light squared on matter to make energy.
Raj: Hey, you totally got that right. E = MC squared.
Penny: I listen. I have no idea what it means, but I listen.