@pb @anildash I don't think you wanted a serious answer but I am going to give you one.
What you are describing is MacsBug! Pre-"X" Macintoshes had a thing you could install that was a sort of CPU debugger. You could get to it with a keystroke, or it would launch if a program specifically requested debugger entry… or if there was a crash! (I forget if it did this by default or if you had to configure it, but I believe it was an option.) When you entered it all normal CPU activity would halt.
@pb @anildash So the idea was supposed to be that if you're a programmer, when your program crashes you could use Macsbug to explore the crash and identify how to fix it. But it was also quite possible to use Macsbug to *undo* a crash, and resume normal operation of a crashed program.
(And sometimes people would just pop in to MacsBug to use the calculator, as it was v convenient. But this became a bad idea once Internet happened, because spending time in MacsBug could confuse the TCP/IP stack)
@pb @anildash MacsBug was like an upgrade for MiniBug— MacsBug was something you installed but MiniBug was built in and could always be invoked with a particular keystroke. But MiniBug was so simple, just a minimal memory debugger, it was unlikely you could ever do much with it.
…And MiniBug was itself kinda like a revamp of the "Monitor" for the Apple 1 and Apple 2, where it was more practical and *could* plausibly recover crashes due to the more predictable memory layouts of the time…