The 21-Second Excitation

The 21-Second Excitation is the eighth episode of the fourth season of the Big Bang Theory.

Plot Summary
Sheldon, Leonard, Raj, and Howard excitedly plan to attend a screening of Raiders of the Lost Ark that includes 21 seconds of never-before-seen footage; However, their plans go awry when Sheldon's nemesis, Wil Wheaton, shows up at the theater. Meanwhile, Penny hosts a girls night party at her apartment with Bernadette and Amy, the latter having never previously attended such a gathering.

Expanded Plot
Sheldon, Leonard, Raj, and Howard excitedly plan to attend a screening of Raiders of the Lost Ark that includes 21 seconds of never-before-seen footage. However, they delay reaching the theater, resulting in much complaining from Sheldon, which becomes worse when Wil Wheaton arrives and is ushered into the theater ahead of everyone. When the four are eventually denied entrance to the theater, Sheldon steals the film cans containing the footage, resulting in an angry mob (led by Wil Wheaton) chasing Leonard, Sheldon, Howard, and Raj out of the theater.

Meanwhile, Penny and Bernadette have a "girls' night in," in Penny's apartment. Amy, who was originally planning on attending the movie with the guys, decides to join Penny and Bernadette claiming "I'm a girl." As Amy has never been to a "sleepover" before, she searches Wikipedia to determine sleepover customs, which Penny and Bernadette reluctantly go along with. During a game of "Truth or Dare," Bernadette and Amy catch Penny off-guard when they ask her personal questions regarding her breakup with Leonard; eventually, Penny storms into her bedroom. In the final scene, Amy discovers that acts of lesbianism are common in sleepovers, and enters Penny's bedroom. The scene ends with Bernadette sitting on the couch listening to Penny's horrified reaction and says she would've been fine with eating raw cookie dough..

Trivia

 * Title reference to Sheldon, Leonard, Raj, and Howard are excited to see a print of Raiders of the Lost Ark, which includes 21 seconds of never-before-released footage.
 * Mayim Bialik became part of the main cast in this episode.
 * Because of her broken leg Kaley Cuoco is shown working as The Cheesecake Factory's bartender again, instead her normal job as a waitress. Also, a body double is used when Penny storms off near the end of the episode.
 * Leonard recalls how Sheldon made him wait in line for Star Trek Nemesis to get good seats, though that film was released in 2002 and Leonard and Sheldon didn't meet until 2003, according to the flashback episodes. Given the tepid response to the film by the public at large it's unlikely there was a revival showing of it.
 * The so-called "submarine controversy" from Raiders of the Lost Ark refers to the scene where Indiana Jones grabs hold to the outside of a Nazi submarine and rides it all the way to their hidden island base. The "controversy" is how Indy knew the sub wouldn't submerge and likely cause him to drown. In novelizations and comic adaptations of the film, The submarine does submerge, but Indy lashes himself to the periscope, which remains above water.
 * The addition of 21 seconds to a Raiders of the Lost Ark special edition echoes George Lucas's adjustments to the Star Wars films, and also calls to mind the South Park episode "Free Hat," in which the boys of South Park try to stop Lucas and Steven Spielberg from creating a special edition of Raiders of the Lost Ark.