The Concerned Man who is seen very briefly asking Chelios if he's okay is played by UFC mixed martial artist Keith Jardine. Jardine is wearing a shirt that says "MEAN 1". This is appropriate as Jardine's in-ring nickname is "The Dean Of Mean".
There is a scene where Chev Chelios attempts to shoot a man cowering on the floor, and when he pulls the trigger and finds the gun empty, utters the line "you lucky bastard!". The same scenario also appears in Snatch. (2000), which also stars Jason Statham, only the antagonist in that scene is Vinnie Jones.
The artificial heart shown in the movie is actually a real artificial heart, the AbioCor from Abiomed. However the real artificial heart is totally internal and does not include a battery box as shown in the movie. The latest AbioCors can run on battery without recharging (done via external RF chargers) for over 4 hours.
Adult film star Ron Jeremy was not originally supposed to be in the porn actors strike in the film. He had assumed that the directors merely forgot to call him and showed up on set. As a result, all of his dialogue was improvised
Just before Chelios rips open the sidewalk electrical box, you can see the 5-star "Obey" logo popularized by Shepard Fairey, the artist who drew the emblematic "Hope" poster of Obama. Fairey got his artistic start with graffiti and by putting up stickers like Obey all over urban landscapes.
The tattooed man Jason Statham rubs up against at the horse track is the lead singer for Linkin Park. He also appeared briefly in the original film as the guy in the hospital pharmacy who tells Chelios about the nasal spray.