Fetish Fuel: The Disney Princess costumes are this In-Universe. The three girls play hookey to go to Disneyland, and get a princess makeover. When Bernadetteis back home, says she has a surprise for Howard, who says "Please be Cinderella". She shows up dressed as that character, and Howard rips his shirt off as they go have sex. When Penny tries to explain why she played hookey, Leonard just sees her dressed as Princess Aurora, and takes off his clothes. Of course Amy dressed as Snow White did nothing for Asexual Sheldon.
Geeky Turn-On: Penny surprised herself at how attractive Leonard became when showing off his holograms.
Then, he almost blows it by referring to Magneto when he shows her an electromagnet.
Hypocritical Humor: While Amy and Bernadette talk to female students about how as women they are expected to just care about their looks rather than their minds, a Reveal Shot shows they are at Disneyland, having just gotten a princess makeover, and Amy is applying makeup. Penny gives them a dirty look.
Mad Scientist: Referenced by Arthur Jefferies/Professor Proton (Bob Newhart) regarding Sheldon.
Arthur Jefferies: Is uh, is he dangerous?
Leonard: Actually he's a genius.
Sheldon: I am.
Arthur Jefferies: That uh, that doesn't answer my question.