The Earlier "Final Sales Version"
There is a "Final Sales Version" of the "Pilot" which predates the generally known broadcast version. The date displayed in the sales version is March 21, 2007. The two versions are largely the same. Most of the scenes in the earlier version have been preserved in the later aired version, except the following two:
The opening scene in the sperm bank: This scene in the sales version is somewhat between the one in the aired version and the one in the "Unaired Pilot". In the sales version scene, both Leonard and Sheldon have made their sperm deposits like in the "Unaired Pilot" scene. But Sheldon thinks they are committing fraud, so he really changes his mind and asks the receptionist Althea for his sperm back. Therefore, the two do not sell their sperm in the end, a bit similar to the scene in the aired "Pilot". The scene in the aired version is a reshoot, evidenced by Althea's longer hair. They all wear the same clothes for the reshoot so that it will match the later scenes in the guys' apartment.
The scene of Leonard driving to see Kurt with Sheldon: The one in the aired version is again a reshoot and slightly longer than the sales one. And the main difference is that Leonard's ex-girlfriend Joyce Kim and her defection to North Korea is only mentioned in the later aired version.
Other differences include:
The name of the show and some other information are displayed in text at the start of the sales version.
The sales version has no opening and closing credits, vanity card and company logo.
The sales version does not have a theme song. Instead, it displays the title "The Big Bang Theory" with an animation of an atom on a yellow background. Two similar animations of an atom without the show title are used between scenes as well.