When Sheldon calls Howard in the car with the words "Red Leader to Red Five" he is imitating one of the X-Wing pilots in the film Star Wars. Red Five was Luke Skywalker's X-Wing call-sign in the first Star Wars movie.
Some reruns of this episode cut out Raj throwing up after Howard throws the walkie-talkie out the window.
When Leonard tells Penny that he has dated four different women since they broke up, he is referring to:
1. Joy - The blind date setup by Bernadette after Leonard claimed the "girlfriend pact" to Howard.
2. Dr. Stephanie Barnett - Met Leonard when Howard invited her to drive a rover on Mars. She was also the only Leonard's girlfriend Sheldon really seemed to like at that time.
3. Dr. Elizabeth Plimpton - Cosmological physicist and pen pal of Sheldon's from Princeton University. She was invited to stay one night at Sheldon's and Leonard's apartment.
4. Priya Koothrappali - At the time of this episode, she was not having a long term relation with Leonard yet. However, she had already spent at least one night with Leonard on a quick trip to LA.