At the AFI Life Achievement Award in 1991 which went to Kirk Douglas, Sylvester Stallone in his tribute to Douglas recalled the filming of the scene where he hits Stallone in the face. After a swing and miss, Stallone jokingly told Douglas to slap him hard. "Let me have your best", whereupon Douglas proceeded to beat Stallone silly. Stallone said "I learned the hard way: never spar with Spartacus".
One night, after filming wrapped, a fire destroyed several sets, many of the actors' trailers (among them Tim Curry's), all of the costumes, and twenty-one valuable vintage cars. Production was halted for two weeks while they were remaking all of the costumes. A Universal security guard hired to guard the cars later admitted to setting the fire.
Kirk Douglas and Sylvester Stallone had only ever appeared in one movie together previously, and it had not been a happy experience. Douglas had started out as Colonel Trautman in First Blood (1982), but quit after a dispute over whether Rambo should live or die at the end. It was not an amicable departure.
When Vendetti (Richard Romanus) is about to leave his office to put a hit on Snaps, he says, "Order out for pizza. We'll be back in an hour." The line is a reference to the actor's work as the "Godfather" in commercial's for Godfather's Pizza.
In the early 80's, the film was originally proposed as another project for director John Landis and star John Belushi, who was penciled in for the Snaps Provolone role. The project was abandoned once Belushi died but resuscitated a decade later, this time with Stallone in the lead.