(at around 12 mins) One of the thugs was shot dead at the beginning of the movie, because the director Ryûhei Kitamura disliked the actor who portrayed him.
(at around 33 mins) In the scene where Tak Sakaguchi's character holds a pistol in his mouth, the director originally called for him to rack the slide with his teeth. He tried this, and broke a tooth. One of the zombies was played by a dentist, and fixed it for him.
In the aftermath of a few of the zombie fights, several zombies' butts are on fire. Director Ryûhei Kitamura did this on purpose, because he just thought it was funny.
Video game producer-director Hideo Kojima (of "Metal Gear" fame) was an extra in the film. Ryûhei Kitamura, as a friend, was later handpicked to direct Kojima's remake of Metal Gear Solid: The Twin Snakes (2004). Versus is attributed to heavily influencing the sword-fighting scenes in the game.
The cast, crew, and director (who call themselves Team Versus) had so much fun making this film that director Ryûhei Kitamura purposely filmed the movie with no ending, with hopes that they would be able to make a sequel. The DVD has proved to be a cult success in both the U.S. and Japan, so Japanese film companies have green-lit the sequel and given it (supposedly) an exponentially higher budget. Team Versus planned on principal photography in mid-2005, though as of August 2018 there have been no further developments.