Yesterday, when I opened my microwave to take out some food I'd been warming, a little cockroach was there to greet me. Inside the microwave. After shooing it out, I forgot about it.

Today, it ( or it's cousin ) was there again. What's going on?

I've heard cockroaches can survive nuclear explosions, so microwaves must be pretty tame. But can they breed  in there?

Also, would they be zapped if I leave the microwave on for a long time?  How long exactly?