The Big Bang Theory
The Big Bang TheoryFacebook/Screenshot

Monday's episode of "The Big Bang Theory," titled "The Expedition Approximation" will highlight some of the troubles that Penny and Leonard go through as a couple, now that their relationship dynamics has changed.

However, this is not the only thing that will keep viewers hooked on to the episode.

Here are a few reasons to watch the 20 October episode of the sitcom.

Sheldon and Raj Bond
There hasn't been many episodes where the relationship between Sheldon and Raj have been explored. But that's all going to change on Monday, when the two will be seen working together in a mine together. As per the official synopsis, "Sheldon and Raj test whether they could survive a dark-matter research expedition in a salt mine by simulating the conditions in a steam tunnel."

However, Penny is doubtful that the duo will succeed. "You guys are going to work in a mine? You had a panic attack when we went through the car wash," Penny says in the video.

Penny and Leonard's Fight
For a while now, Penny and Leonard have been bickering over how she handled her finances, and on Monday, the couple will finally seek advice from Wolowitz and Bernadette after they fight about money.

But Wolowitz and Bernadette might not be the ideal pair to dole out relationship advice, as the promo photos show the couple too hasn't figured out how to deal with monetary issues.

In a scene from the teaser video, Leonard is seen getting offended when Penny points out his insecurity. "I can't believe you'd say that," he tells Penny. "You know how insecure I am about my insecurities."

Sheldon-Amy Relationship: Ever since the famous Sheldon-Amy kiss in the previous season, fans of "Shamy" have been eagerly waiting to see their relationship progress. But to no avail.

On "The Expedition Approximation," the couple is expected to have a moment when Amy tries to prevent Sheldon from embarking on the expedition. But in true Sheldon style, he is going to scoff at Amy for displaying human emotions.

"The Big Bang Theory" Season 8, Episode 6 will air on Monday at 8pm ET on CBS.