Our friends of the OKRA! dropped off a bat costume later that day, too. It had belonged to their son and he had outgrown it.
When Connor woke up the next morning and saw the costume, he immediately wanted to put it on. And he kept it on most of the day, though I did make him take it off for meals.
The next day it was the same story. Incidentally, he also missed his nap that day. Which allowed me to get this picture:
Guess we know what he's going to be for Halloween this year!