The full game was given out for free on the December 2001 issue of Gamelive PC, a Spaniard computer game magazine.
Banned in Germany because of extreme violence and human enemies. As an interesting sidenote, Kingpin was debated heavily in Germany due to a controversial ad Interplay published in all major gaming magazines, depicting a row of bodybags and the cynical line "You can get used to it".
The majority of this game's boss characters are modelled after various gangster/gangsta/pop culture movie characters. The first boss, The Jesus, screams out lines taken from the character of the same name from The Big Lebowski. Heilman, another boss, sounds EXACTLY like Dr. Strangelove and even screams out such lines as "Mein Fuhrer, I can't walk!". Blunt and Tyrone use various lines from pulp fiction, and The Kingpin himself looks like Pulp Fiction's Marsellus Wallace and even uses a good deal of that character's lines.
Ryan Feltrin, the AI programmer (also known as "Ridah") is famous for his previous work on Quake / Quake2. He is the creator of the very original QuakeRally for quake and of the infamous Eraser deathmatch bot for Quake2
Kingpin features several tunes from Cypress Hill
The bugs in the original release of the game earned it ridicule from gaming magazines. Some of the more infamous ones include an enemy running after you in a tunnel and getting stuck on a single pixel so that he runs in place; another is a stationary enemy that, after getting shot but not killed, runs around in a circle endlessly.