The main storyline begins when Sheldon and Leonard run into at a drug store. Conflict arises when Arthur emails Leonard to collaborate on a research paper about vacuum nanoelectronics instead of Sheldon, whom Arthur finds incredibly annoying.
: Sheldon is seen wearing a Sinestro Corps (Yellow Lantern) shirt, which symbolizes "fear"—a nod to the tension in his relationship with Arthur during the episode. [S7E7] The Proton Displacement
: Meanwhile, Raj joins the "girls' night" with Penny, Amy, and Bernadette to make jewelry. Howard crashes the evening, using his high-tech tools to "improve" their crafts, which upsets Raj, who feels his safe space for expressing his feminine side is being invaded. Cast and Key Guest Stars The main storyline begins when Sheldon and Leonard