It's all about relationships on The Big Bang Theory Season 8 Episode 12.

Sure, it is filled with plenty of hilarious quotes and great comedic timing, but there's so much more going on than a few good laughs. In many ways, "The Space Probe Disintegration" is a pivotal episode.

When Penny and Amy arrive to spend a day with their guys, Sheldon assumes they'll do what he wants and play Lord of the Rings Risk (okay, that does sound sort of fun) all day long. They refuse and are able to convince Sheldon and Leonard that for a change, they should be the ones to pick their activity.

What this results in is a completely cliche outing where Penny and Amy try on clothes and Sheldon and Leonard sit around and wait for them. Heck, they even hold the girls' purses. This isn't exactly quality time for all four of them, and you have to wonder why Sheldon and Leonard didn't just get to stay home. But, what this outing does is creates an opportunity for some important realizations.

Sheldon and Leonard find themselves arguing over who makes the most compromises, which quickly becomes a touchy subject. The running joke is always how much Leonard takes care of Sheldon and plays along with his "Roommate Agreement" rules. Now that Leonard and Penny are engaged, they've been wanting to move in together. After Sheldon took off at the end of last season, though, they haven't been planning on that any time soon. By the way, I'm glad this is brought up again, as opposed to just letting it drop.

Do you realize I don't live with the woman I love because of you? Leonard Permalink: Do you realize i don't live with the woman I love because of you?

Permalink: Do you realize i don't live with the woman I love because of you?

The guys have an emotional talk about Leonard moving out, complete with tissues. What's decided is that Leonard will move out gradually so that Sheldon can adjust. At the end of the day, Sheldon may be frustrating, but Leonard is always going to be there for him. The decision works well, because it allows Leonard and Penny's relationship to continue to develop while maintaining the roommate dynamic of the show.

There's also an important change for Penny and Amy, when Penny realizes Amy makes sacrifices for her all the time. It's sad; Amy says she does it because she's grateful to have a friend in the first place.

Other thoughts:

Howard and Raj have a surprisingly serious conversation about religion, which lets us see a new side to each of them.

Bernadette isn't very present in this episode, but when she is, she makes it count. I love her more and more each week.

Sheldon and Leonard dealing with smart phone withdrawal in the store is probably my favorite moment.

Sheldon: There were plenty of ways to pass the time before smartphones were invented.

Leonard: That's true.

Sheldon: I'll look them up... Oh, son of a biscuit! Permalink: I'll look them up... Oh, son of a biscuit!

Permalink: I'll look them up... Oh, son of a biscuit!

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Ashley Bissette Sumerel was a staff writer for TV Fanatic. She retired in September 2017. Follow her on Twitter and on Google+.