Alright, this works for any dog, or even your baby, but you will need a bathroom to do this. Simply put a dog/baby in front of your bathroom door, and then go in.
It may take a few attempts to get it right though.
So if you get it right, you'll pick up your baby/dog and go in at the same time.
If you useda dog, the dog should be right above your bathtub, watching you...
If you used a baby, you'll come out of the bathroom, still holding the infant, but now the baby is invisable.
To regain sight, just put the baby down.
To reclaim your dog, press A while near the door, but don't go in. Whistling tends to make it a bit easier.