I really don't think they do anything out of spite....except if you have 2 and one will steal the toy from the other
I keep my carpet rooms CLOSED off because even at 3 Cheri still likes to sneak in and pee on carpet ....
as far as hiding treats and things - My Chanel is FIVE years old and hides stuff ALL OVER MY HOUSE....She is so serious on her hiding places and puts alot of thought into each one ....if you DARE to look at what she hid - she'll MOVE it LOL...She has big fun checking her stashes throughout the day
it's a yorkie thing and I think it's totally CUTE CUTE CUTE !