The segment with the rocket powered car features MythBusters (2003) host Jamie Hyneman and Adam Savage as the surplus salesman. The first episode of 'MythBusters' dealt with that particular urban legend.
After Siri and Michael argue in the café and Siri storms off, the book-reading couple Michael briefly talks to are played by Winona Ryder's real-life parents, Michael and Cynthia Horowitz.
The scene involving the JATO rocket is not the only "Mythbusters" connection in the film. Adam Savage and Jamie Hyneman also examined (and debunked) the story of the ice fishing with dynamite mishap in a subsequent episode of Alaska myths. Additionally, the "pulley" sequence with Michael and the filmmaker sliding up and down the building face on a rope is a slightly-altered retelling of the "barrel of bricks" myth which Adam and Jamie also investigated (and found somewhat plausible if highly unlikely).
The title is based on a real set of awards given to people who inadvertently "help" natural selection by acts of sheer stupidity that result in their removal from the gene pool, either by their death or any other act that makes them incapable of reproducing.
Metallica are performing their song "Sad but true" in the film. It was recorded at a regular live show in Salt Lake City on November 22, 2004. The show was interrupted during "Sad but True" but the song was only played once. To celebrate the premier of the movie at the Sundance Film Festival on Wednesday, January 25, 2006, the band played at a private party following the screening that day.