Interesting. Even before I saw the BBC series on TV, not exactly how I pictured it. Don't think Adams did either in the book did he?
Kenny Bunkeport's description-more of a cigarette lighter or a pez dispenser would be more accurate. I never really could tell how Adams invisioned it from the script. I was thinking something like the way the multi-headed creature that Johnny Knoxville played in MIB2 would be it. It never said bot heads were active at all times, did it?