How to make someone (but not their clothes) disintegrate

I was thinking more of constructing the dummy from balloons filled with hydrogen and oxygen. :-)

That reminds me of Pepper's Ghost, which requires a glass sheet at 45 degrees to the audience (either vertically or horizontally) and the lit up dummy is at 90 degrees behind a curtain so that the audience see only the reflection. Switch off the light and the image disappears, perhaps being replaced by a pile of clothes at the image position then being lit up.

Does the stage have a trapdoor? The skeleton inside the clothes could be dropped through the trapdoor, but the clothes prevented from going through by strings, in such a way that the pile of clothes would hide the trapdoor.

...which can be very effective but requires, as you say, an elaborate setup and strict lighting control, neither of which are feasible for the brief effect I'm after.

Thanks for the thought, though. I'd love to try a Pepper's Ghost-based effect sometime, but sadly this particular time isn't the one.