The wad of bills that O'Donovan finds in Duane's room was the vast majority of the films budget. Later, additional funds were needed to complete post-production and blow-up the negative from 16mm to 35mm.
When Analysis Films first released "Basket Case," they cut it. They removed most of the gore so the film would be "funnier." Obviously, the gore is part of the punch line so their cut version was awful, few came to see it, and the film died almost the moment it was released in April of '82. However, "Drive-In Movie Critic" Joe Bob Briggs wanted to host the Dallas premiere of the film in June but wouldn't host a cut version. So Analysis sent it to Dallas uncut and let it play there. The film quickly started selling out. So Analysis quietly replaced the cut version with the uncut version everywhere else and the film suddenly became a hit. After three weeks of the uncut version playing in New York's Waverly Theatre in Greenwich Village, Analysis finally put an ad in the Village Voice announcing that, yes, it's finally uncut.
Most of the credits that appear on the end of the film are fake. The crew was very small and rather then repeat the same names over and over again they decided to just make up names.
The Bar scenes were shot in a S&M club in Manhattan which is now a fancy restaurant. The bar was so big that they also used it as the Bradley's basement and the crew had to hide all the sex toys including a large swing (which was still in the club until the day it closed). The original buzz saw used to kill Duane and Belial's father used to hang above the door of the club until it was eventually stolen.
Most of the Hotel Broslin interior set was constructed at the loft of artist Ugis Nigals on the 6th floor of 15 W. 18th Street, NYC. The sets included Duane's room, Casey's room, O'Donovan's room, and a chunk of hallway. The lobby was in a doorway on Franklin Street with the check-in desk constructed in its elevator. The large stairway of the hotel was also in the Franklin Street location. And the hotel sign Duane and Belial hang from was attached to the fire escape outside Kevin Van Hentenryck's loft on Hubert Street.
Most of the crew left the scene involving Belial and Sharon. The crew didn't seem to mind until the blood was added which is when they got all uppity and offended. So Edgar Ievins operated Belial and Kevin Van Hentenryck helped with the lighting. Pretty much the same thing happened with the "blowjob" scene in "Brain Damage."
The scenes with Duane streaking where shot in the area now known as Tribeca but, back then, it was a fairly nondescript area of industrial buildings that was damn near deserted at night. Nevertheless, the crew got Kevin out of there as fast as possible just in case anyone saw him.