This is a real Derpy Snowglobe from S2E18 : A Friend In Deed. I'm shaking it so you can see Derpy move around. She actually moves nicely, I don't know what happened here. You can see still pictures on the link below.
It's on eBay here : http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120925272540
Picture here : http://bulldogs29.deviantart.com/#/d525ryx

Sorry for the lousy video. I was just trying to get her to stay in the camera view so you could see her floating around.