I've been playing a game today. In it is a household with toddlers - and a few gnomes. Without thinking too hard of possible consequences, I put a teddy bear in each cot so they would get the extra 20+ Lifetime Reward Points while sleeping.
Three of them aged up to children and I only could find the toy belonging to two of them, so I put their teddy bears in their respective inventories and had a look around for the other one and couldn't find it. There was another bear I'd put on the floor for them all to play with and it was gone too. So I got a new teddy bear for the one child who was missing theirs and put it into their inventory.
Then I went to the cot where the remaining toddler was sleeping. I could see his teddy bear still in the corner of his cot and grabbed it to put into his inventory and realised it was not a teddy bear at all. It had become a vampire gnome. It gave me a bit of a chill. I put the gnome on the floor and got him a new gingerbread bear from buy mode and put it into his inventory.
He ages up today so hopefully if he keeps the thing in his inventory from now on it won't turn into a vampire gnome. I noticed the children get the 20+ moodlet while sleeping with a teddy bear in their inventory.