The author of this sentence chose to leave out the preposition 'in' before the phrase 'in the moment' which kind of throws me off. I can't make friends with it.Is there are rule behind it?
I always dreamed that I would own an amazing animal like this someday; a huge teddy bear that can wrestle playfully with children one moment and in the next, snap to attention at the owner's command and be the protector
Here is another way to write it:
...One moment it is a huge teddy bear that can wrestle playfully with children.
The next moment it snaps to attention at the owner's command....