We have given DS fish- easy hid in the shed for a couple of days before.
My DH gave me a kitten for Christmas, hid at a friends house, on Christmas Day I opened a big box full of all things for kitty. Then went to friends and picked her up.
Last year we gave DS2 chickens. DH had built the hen house over a few nights when the kids were in bed or I took them out looking at lights, then we hid it up the side of the house and on Christmas Eve picked up chickens from a friends house once the kids were in bed.
This yr DD is getting a bird. I am picking him up tomorrow and hiding him at yet another friends house (we share the love around lol) then once the kids are in bed Christmas Eve I will go and pick him up.
Disclaimer: all pets given were much wanted pets and we are responsible pet owners who know a pet is for life not just for the holidays