@nyrath @FredKiesche Nope: Varley's Symbs predate The Ophiuchi Hotline—they showed up in his earlier Eight Worlds stories ("Gotta Sing, Gotta Dance" won a Locus Award in 1976). Predate "Doorways in the Sand", and very different from the Heinlein "Puppet Masters" (although that's clearly where Futurama's Brain Slugs come from).