Kittens being abandoned in boxes seems to happen pretty regularly but it's never happened to me! I've been handed a box of kittens found under a bridge, but never actually found a box myself.
The kittens were adorable BTW. We flea-treated, combed and wormed them, gave them plenty of good food and let them cause chaos in the house while we found them a rescue space. They went off to an experienced rescue and I spent a day cleaning up.