You know how after you have popped some popcorn you are STRICTLY not allowed to put the unpopped bits back in the microwave and try again, well why is that? Every time I go to do it everyone yells “AARRGGHH, NO DON’T DO THAT!!!”
What on earth happens if you do??
Nothing happens. They just burn (along with the rest of the popcorn if you put them in all together). At the point you are talking about, the popcorn that is going to pop has popped (for the most part). Any unpopped kernels remaining don’t have enough water left in them to pop. Probably the reason they didn’t pop is that there was a hole or crack in them that allowed the boiling water to escape slowly, rather than explosively. I think the reason that most people yell at others for even trying this is that those unpopped kernels are quite tasty. 
“AARRGGHH”?
Do your freinds eat PEANUTS[sup]®[/sup] as well?
Yeah, I know I’m hilarious… 