He or she looks like this now:
The kids named him/her Oreo, even though I objected to it being an unoriginal name! I didn't get a picture of the black one before, but he was smaller than the Oreo.
They named him Eightball. He's the runt of the litter.
He's doing pretty well too! The mama is feeding them twice a day, and we are keeping them outside her cage when they are not eating.
The kids love them, and want to keep them... but they will be going back next week. We have enjoyed them while they are here, though! :)