This episode introduces Mayim Bialik as Amy Farrah Fowler, Sheldon's love interest. Bialik would become a show regular the following season. It also marks the final appearance (so far) of Sara Gilbert as Leslie Winkle and the first appearance of Brian Thomas Smith as Penny's dim bulb of a new boyfriend, Zack.
For one of the few times in the series, Leonard gets drunk.
Raj reveals that The Good Wife is his current favorite TV program.
The title refers to the lunar experiment that the guys conduct in the episode.