It was Dahl's first book and was written for Walt Disney Productions, in anticipation of a feature-length animated film that was never made.[Note 1] With Dahl's assistance, a series of gremlin characters were developed, and while pre-production had begun, the film project was eventually abandoned, in part because the studio could not establish the precise rights of the "gremlin" story, and in part because the British Air Ministry was heavily involved in the production because Dahl, who was on leave from his wartime Washington posting, insisted on final approval of script and production.