I guess I made a mistake in letting my daughter pick out the hamster she wanted.
Today I looked in its cage and thought it was swarming with giant maggots. Apparently, Pikachu is female.
It takes about three weeks before the babies develop (right now they're hairless and their eyes haven't opened) but apparently it's common for young hamsters to eat their entire litter.
We haven't told my daughter until the babies are too big for a quick meal.