Just tried this out in one of my projects, here’s what happened:
do something works without a problem.
do something else never goes off.
the rest of the game keeps running as normal. You can even call foo() again any number of times and do something will still go off.
Having it waiting in the background didn’t seem to have much of a performance impact. I started 5000+ of them and foo() only took up ~0.6% frametime with the rest of my game running alongside it.