Dick Miller started on this movie, but he was recast after a bike crash left him with several broken ribs.
Though wildly miscast as the gang's leader, Cassavetes nevertheless accepted the part because he needed the money to fund post-production on his own film Faces (1968). Ironically, his next picture, The Dirty Dozen (1967), paid him a great deal more, which might have made him think he should have waited a little before accepting this role.
The poster on the inside of the clubhouse door is of Marlon Brando in The Wild One (1953), with a beard drawn on it.
When the Skulls MC decide they want revenge on the town, they enlist the aid of the Stompers MC, a much larger biker gang. This alludes to another film also released by AIP, The Glory Stompers (1967), in which Dennis Hopper plays Chino, the leader of the Black Souls.
Cody likens their situation to that of Butch Cassidy and the Hole-in-the-Wall Gang. This film was made two years before Butch Cassidy and the Sundance Kid (1969).