Things I have learned about puppies:
They might go into the laundry and sleep by themselves all night in the dark. And they might even pee on the paper. But they reserve the right to chew up the bottom of the door to the toilet in reply.
They really do eat your homework.
They grow up a lot in a short amount of time. 3 weeks really is like 21 in puppy time. I've caught myself starting sentences to her with: when you were *little*, 3 weeks ago ...
They still do eventually get tired.