backfire on 4-cyl

[CTGT1]

So a friend of mine as a 4-cylinder sunfire (I'm not sure if it's a 2.2 or a 2.4 I haven't asked), and she was worried because, from her description, 'the muffler made a loud pop shortly after I turned the car off.'
Which obviously sounds like it backfired (fuel was too rich for whatever reason). But does anyone know whyy this would happen AFTER she turned it off?
If you have any ideas, let me know
-John

[mr_eh]

hmm was she revving it at all?

when i rev it and let it come down to idle it sounds like the last 30 seconds of popcorn being made when all the kernels decide to pop at once *sigh*

my ghetto als...