Solar Opposites did it very well when they jettisoned Justin Roiland. His character gets hit in the throat with a dart and then zapped with an uncalibrated voice repair ray. His partner thinks the new (and suddenly English-accented) voice is sexy so they don't bother changing it.
Also, new Korvo is way better the than slightly-altered Rick that Roiland was crapping out.
It's one of the easiest high-energy reactions to prepare, contains only very stable powdered iron and aluminum (though you can add other things as buffers to slow the reaction, such as boron or carbon) and it can only be kicked off by VERY intense heat, like from burning magnesium or the burning titanium powder in a sparkler. Thermite can be shipped through the mail with no special considerations. Were you thinking of something else?