Penny is revealed to have a Chinese character tattoo on her right buttock. Kaley Cuoco, who plays Penny, has an actual Chinese character tattoo on her lower back, as seen in the episode, The Middle Earth Paradigm (2007).
In this episode, Kunal Nayyar displayed his ear for accents when he accurately imitated costars Johnny Galecki's and Simon Helberg's American accents.
This episode mirrors The Vegas Renormalization (2009), with Leonard, Raj and Howard being away while Sheldon and Penny stay at home. The reversal is that this time, Penny is the one who is "kind of sick", and Sheldon having to sing "Soft Kitty" to her (and Penny makes him start over several times).
The coordinates Raj gives for the observation site (34.48 N, 118.31 W) refer to the Vasquez Rocks Park, the location of several Star Trek episodes including the one where Captain James T. Kirk rolls a rock onto the reptilian Gorn. A Gorn later make appearances in two of Sheldon's dreams (once in The Apology Insufficiency (2010) in Season 4, and again in The Transporter Malfunction (2012) in Season 5). Also the gang makes one more visit to Vasquez Rocks Park in Season 6's The Bakersfield Expedition (2013) where Leonard gets his car stolen while the gang were taking pictures acting out scenes from Star Trek.
This episode marks the first time Soft Kitty had been sung to anyone other than Sheldon.