The ringtone on Howard (Simon Helberg)'s phone is Thomas Dolby's "She Blinded Me with Science", the same song used as the theme song in the Unaired Pilot (2006), the original pilot that CBS passed on. Dolby's song was a perfect choice, as his early 80's geeky nerd persona was much like the Big Bang gang.
While checking out Howard's tweets, Leonard calls them "twitters". While this may sound odd now, at that time that's what they were called. Not long after this was originally aired Twitter began to officially call them tweets.
Raj cites his full name for the first time and we learn his middle name is Ramayan in this episode.
UK TV channel E4 - which airs The Big Bang Theory (2007) in rotation - has never aired this episode in its daytime slots because of its prostitution storyline.
When Penny is playing twenty questions with Sheldon, she makes her standard game guess of "Star Wars" since she doesn't understand their Sci-Fi universe.