The term originated in the animated television series South Park. In its typically hyperbolic style, the show satirized attorney Johnnie Cochran's closing argument defending O.J. Simpson in his murder trial.
The term Chewbacca Defense was first used in the South Park episode "Chef Aid", which premiered on October 7, 1998 as the fourteenth episode of the second season.
In the episode, Chef discovers that Alanis Morissette's hit song "Stinky Britches" is the same as a song he wrote years ago, before abandoning his musical aspirations. Chef contacts a "major record company" executive, seeking only to have his name credited as the composer of "Stinky Britches." Chef's claim is substantiated by a twenty-year-old recording of Chef performing the song.
The record company refuses, and furthermore hires Johnnie Cochran, who files a lawsuit against Chef for harassment.
In court, Cochran resorts to his "famous" Chewbacca Defense, which he "used during the Simpson trial", according to another South Park character. Aside from reading a portion of his defense below, you can also listen to it here.
Cochran begins by noting that although Chewbacca is from Kashyyyk, he lives on Endor, and then proceeds to the heart of the defense:
Why would a Wookiee, an eight-foot tall Wookiee, want to live on Endor, with a bunch of two-foot tall Ewoks? That does NOT MAKE SENSE! But more important, you have to ask yourself: What does this have to do with this case? Nothing. Ladies and gentlemen, it has nothing to do with this case! It does NOT MAKE SENSE! Look at me. I'm a lawyer defending a major record company, and I'm talkin' about Chewbacca! Does that make sense? Ladies and gentlemen, I am not making any sense! None of this makes sense! And so you have to remember, when you're in that jury room deliberatin' and conjugatin' the Emancipation Proclamation, (approaches and softens) does it make sense? No! Ladies and gentlemen of this supposed jury, it does NOT MAKE SENSE! If Chewbacca lives on Endor, you must acquit! The defense rests.
Cochran's use of this defense is so successful that the jury finds Chef guilty of "harassing a major record label" and sets his punishment as either a two million dollar fine to be paid within twenty-four hours or, failing that, four years in prison.
Ultimately a "Chef Aid" benefit concert is organized to raise money for Chef to hire Johnnie Cochran for his own lawsuit against the record company. The concert (a parody of Live Aid) features his old showbiz friends — Elton John, Meat Loaf, Ozzy Osbourne (who kills Kenny by biting his head off), and others (the real-life artists recorded songs for the episode and accompanying album). At the concert Johnnie Cochran experiences a change of heart (à la How The Grinch Stole Christmas) and offers to represent Chef for free. He again successfully uses the Chewbacca defense, this time to defeat the record company and make them acknowledge Chef's authorship of their song. In the second use of the Chewbacca Defense, he ends by suddenly producing a stuffed monkey and shouting "here, look at the monkey. Look at the silly monkey!", causing a juror's head to explode.
Interestingly enough, Chewbacca does not in fact actually live on Endor — though early drafts of Return of the Jedi did have the forest moon of Endor populated by Wookiees rather than Ewoks. This claim may have been an error, or may simply have been a culturally savvy intentional mis-statement by the authors. Parker and Stone have included numerous Star Wars references in South Park episodes, and are aware that the Wookiee homeworld is named Kashyyyk, despite - at the time the episode was made - the name having only ever been given in Star Wars books and games, not the movies. (Kashyyyk was subsequently shown as the Wookiee homeworld in Revenge of the Sith.)
Also, Cochran calls for an acquittal, when such a result is impossible in a civil case (where there can only be a finding of liability or no liability). In any event, he is initially representing the plaintiff record company, and is therefore seeking to persuade the jury to find Chef liable - the civil equivalent of a conviction, and not an acquittal.
The term Chewbacca Defense is used on many weblogs and Internet discussion forums, especially ones that often feature legal issues. Slashdot is one such example, where the Chewbacca Defense has been occasionally mentioned in discussion of legal affairs where the poster feels the legal arguments make no sense (or alternatively where the poster feels the argument of another is similar to the Chewbacca Defense. See also Slashdot subculture. Still within the realm of the Internet, the Chewbacca Defense has been applied to political subjects, especially concerning public figures attempting to distract or confuse the public through the media.