Herek began a friendship with Muir while working as assistant editors on "City Limits" (1985). When Herek was looking for his next project, Muir offered him his screenplay for "Critters", which he had written three years earlier. After working on the script, he pitched it to Sho Films because of an existing working relationship to get advice on how to get the film made, in which their executives agreed to develop it. Principal photography began in Valencia, California in July 1985 on a six-week shooting schedule.