Amy finds out that Sheldon applied for a one-way trip to Mars on The Big Bang Therapy. "The Colonization Application" is the 17th episode of the show's eighth season.
Leonard and Raj run into a restaurant customer who looks just like Nathan Fillion. "The Comic Book Store Regeneration" is the 15th episode of the show's eighth season.
The girls remember some of their most embarassing moments on The Big Bang Theory. "The Troll Manifestation" is the 14th episode of the show's eighth season.
Sheldon and Leonard go dress shopping with Penny and Amy on The Big Bang Theory. "The Space Probe Disintegration" is the 12th episode of the show's eighth season.
Raj and Sheldon head into a steam tunnel for an experiment on The Big Bang Theory. "The Expedition Approximation" is the sixth episode of the show's eighth season.
Sheldon [to Kripke]: Also, I am given to understand that your mother is overweight. Raj: Oh, snap. Sheldon: Now of course, if that is the result of a glandular condition and not sloth and gluttony then I withdraw that comment.