5. The Big Bang Theory, "The Terminator Decoupling" (Season 2, Episode 17)
The Big Bang Theory is one of the highest-rated sitcoms on television, and it's such a part of the pop-culture zeitgeist these days that I'd wager you'd be hard pressed to find someone who's never seen an episode. But just in case, season 2, episode 17 is the place to start. Like many sitcoms, Big Bang really hit its major creative stride in season two, and The Terminator Decoupling is a perfect example of the sort of television that stride produced. The episode encapsulates everything fans love about the series in 22 minutes. When taking a (Sheldon mandated) train journey to San Diego for a conference, the guys realize that geek girl Summer Glau is on the train with them. While Leonard, Howard, and Raj moon over Summer, Sheldon panics over a scholarly paper he's left behind. As you might expect, hijinks ensue in all quarters. The episode works so well because it plays to the strengths of the show. On one hand there's the hapless-in-love guys jumping through all sorts of hoops to impress the geek guest star, and on the other there's the borderline obsessive Sheldon desperately trying to walk Penny through accessing and delivering his paper to him via email. Hilarious as both the A and B stories in the episode are, they also provide insight into each of the characters along with the laughs.