The first time Mega Man was vaporized, it was something of a shock. When he suddenly reappeared after apparently being vaporized, it was surprising but not unwelcome. The second time he was vaporized, it was funny, if only because of the repitition. So clearly, following the rules laid out earlier, Mega Man's second return after apparently being vaporized should also be funny. However, if my math is right, he can only be vaporized one more time before the joke becomes too stale to use again. After all, the reader should be expecting him to be vaporized this time, and half the fun in any joke is the surprising the audience with the unexpected.
You know, I never did properly explain how Mega Man kept surviving Bob's blasts. I mean, the joke is basically that he's blown clear, but how? One idea I was toying with at the time was that, as a video game character, Mega Man has extra "lives", and he's simply using them up each time he gets blasted. Of course, that doesn't make any sense considering he keeps coming back scorched, darker after each blast. But then, since when did anything ever make sense in this comic?