 According to the DVD commentary, the scene where The Spleen (Paul  Reubens) accidentally ignites a blast of flatulence standing by a  barrel with a fire in it, was a happy accident. Apparently a crew  member had tossed a plastic lighter in the barrel. It happened to  explode (a small explosion, but an explosion) while filming on  Reubens. The reactions that followed were created after the fact,  capitalizing on the moment caught on film.