The Heavy Metal promotional machine usually featured the concept artwork of a major motion picture that was (entirely by coincidence) advertising in the magazine. The editors of the publication were pretty good about trying to feature material that would appeal to the readers. In this case, Brian Froud’s work fits into the overall visual schema fairly well.

I think one of the reasons that The Dark Crystal didn’t get the box office draw from Heavy Metal readers was the lack of any obvious sex interest in the promotional material.

(Heavy Metal issue #70, January 1983 – Page 63 Gallery: The Dark Crystal: The Twinkle in Brian Froud’s Eye by All)