The Mercedes that chases Paul and Ben had to be modified for filming, since that brand of car does not swerve very well in high-speed pursuits.
When Robert De Niro is singing "I Feel Pretty", the lyrics used are those from the original stage version, as opposed to the film version of West Side Story (1961). The lyric "I feel pretty and witty and gay" is changed back from "gay" to "bright".
Paul's main nemesis is named Ragazzi, which in Italian means "boys".