Superman

The boys held a Superman movie marathon and invited Penny, who surprised them by asking how many Superman movies there were ('Five!'). The boys then launched a debate about whether Superman's rescue of Lois Lane in the first film was scientifically accurate, a debate which began with this wonderful exchange:

Sheldon: You realise that scene was rife with scientific inaccuracy.

Penny: Yes, I know, men can't fly.

Sheldon: No, let's assume that they can ...

The debate ended with Penny retreating into her apartment and the boys discovering they'd locked themselves out of theirs. Sheldon was wearing a Superman t-shirt for the movie marathon. Leonard has 2600 Superman comics in the apartment. (0102)

We also learn that Sheldon believes that superman's flight ability is a "feat of strength" for which he requires "Earth's yellow sun". At night, according to Sheldon, superman's flight energy derives from "a combination of the Moon's solar reflection, and the energy storage capacity of Kryptonian skin cells". Leonard, Howard and Rajesh do not believe in the existence of Kryptonian skin cells (0102). A similar debate can be found amongst superman fans in various online forums.

In (0109) Penny finds out that Leonard has a model of the bottled city of Kandor in his bedroom closet. For information on Kandor see wikipedia.

Superman villain Zod is mentioned in episode (0113).

The boys debate how Superman could clean his uniform from indestructible 'Kryptonian sweat' (0211).