"The Big Bang Theory" delivers a hilarious episode Thursday night, with the return of Sheldon Cooper's idol and new friend, the Stephen Hawking.

Guess who is playing Zynga's "Words with Friends?" And what is Penny up to?

Spoiler Alert: This article contains spoilers for those who have not seen the Season 6, Episode 6 installment of The Big Bang Theory: "The Extract Obliteration"

Here are the highlights of this week's 'Big Bang' episode:

1. A new bonding is moving up the stages of friendship - Sheldon Cooper and the Stephen Hawking play Words with Friends.

2.  Coop and Rolling Thunder are now pet names TBBT fans might hear every now and then.

3. Raj and Howard plays accent-off. You have to hear it to believe it. It's like the good old days for these buddies.

4. Penny returns to school, but she doesn't want anyone to know. Leonard eventually finds out.

5. Penny realizes again that she is not really Leonard's ideal girl in the academic background criterion.

6. Sheldon tries some Jedi mind tricks like a very needy new friend.

7. Bernadette and Amy help out Penny, but she refuses same help offer from Leonard. The girls feel like it's high school all over again.

8. Sheldon deals with Hawking's "sore loser" situation.

9. Leonard reads Penny's paper, and comments, "She writes like she cooks." Penny gets a B+ for her paper.

10. Sheldon has something in common with a black hole. They both suck, according to Stephen King. (Only Stephen King can do this to Shelly and get away with it!)

Best Quotes from TBBT S06xE06: "The Extract Obliteration"

You guys have got to be the weirdest couple I know. -Amy
Really? You can't think of anyone weirder? -Penny
I can, but she's sitting right there. -Amy

Play, play, play, play. -Sheldon

What are you doing? -Leonard
Trying to use a Jedi mind trick to control Stephen  Hawking. Ugh, he must be wearing a tin foil hat or something. -Sheldon

I feel like we're in high school again. -Amy
I know, doing the prom queen's homework so she'll finally like us. -Bernadette
I know, it's finally working. -Amy

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