Coen Brothers alum John Turturro and Evil Dead actor Bruce Campbell were both given the chance to play Edgar the Bug, a giant cockroach alien in disguise and the main antagonist of the first film, but both actors declined and the role eventually went to Vincent D'Onofrio.
An animatronic version of Edgar the Bug was created for the final scenes of the original film, but the producers opted to use a computer generated bug instead, an investment that took up $4.5 million of the film's budget.
According to The Humane Society, no cockroaches were harmed in the making of the films. The yellow goo that can be seen when Agent J stomps on the bugs was actually created using packets of mustard, and the cockroaches were all accounted for at the end of every day on set.