Say I have some function foo.

Consider snippet A:

args = # some args
foo(*args)

And consider snippet B:

import threading
args = # some args
thread = threading.Thread(foo(*args))
thread.start()
thread.join()  # yes, I do mean to immediately join after starting

I want to know what sorts of things (if anything) I could do in foo such that A and B behave differently (eg crash or different run time).

The thought experiment serves to hopefully answer my main question.