It being the frivolous season, a memory came to mind of Claude Shannon's "spooky hand in a box" toy, or which apparently was sometimes called the "Ultimate Machine". For those not already guffawing in an "I remember that" moment, here's a description pilfered while I was searching the web: Arthur C. Clarke in 'Voice Across the Sea': "Nothing could be simpler. It is merely a small wooden casket, the size and shape of a cigar box, with a single switch on one face. When you throw the switch, there is an angry, purposeful buzzing. The lid slowly rises, and from beneath it emerges a hand. The hand reaches down, turns the switch off and retreats into the box. With the finality of a closing coffin, the lid snaps shut, the buzzing ceases and peace reigns once more. The psychological effect, if you do not know what to expect, is devastating. There is something unspeakably sinister about a machine that does nothing -- absolutely nothing -- except switch itself off." (The one I remember was a plain black cube, not a coffin.) It was a popular gimmick-toy / party-amusement in the sixties (I think I saw it at Xmas/New Years time), but I haven't seen, heard or remembered it for decades. I'm just curious whether they are still being made or are they all gone, except perchance to find one at a garage sale (ebay?)? Is this recognisable to anyone younger than ~35, or is it a forgotten amusement from the past? What does this have to with computing? As stated it was devised by Claude Shannon, in discussion with Marvin Minsky, and that should be enough, but I'd also guess that it came out of thinking about things like the halting problem, minimal machines, etc. (a machine that does nothing but halt itself...). (Every computing museum should have an original one.)