The girl who played Penny's ex-boyfriend's girlfriend was Kaley Cuoco's younger sister Briana Cuoco, who choreographed the Big Bang flash dance performed for the studio audience as is available on YouTube.
The QR code on the side of the front counter at Stuart's comic shop maps to www.thecomiccenter.com. As of 2021, the site no longer functions.
Alex bought a map of The Canterbury Tales for Amy because it is one of her favorite books. Amy can be heard quoting from this book during the girl's night in The 21-Second Excitation (2010).
Last appearance of Dale (Josh Brener). Although he seems like a regular customer of the Comic Book Shop, he only appeared in The Flaming Spittoon Acquisition (2011) and this episode.
In a rare "proper' display, the 4-section hazard warning sign on Howard's lab door is oriented correctly, and has value numbers in each field. It is usually off-set by 90°, showing no numbers.