So basically the golden trio are in the common room and end up talking about the Winter Ghost. At first they don't believe it but then with some frost and snowballs they get suspicions, then in the end the ghost turns out to be none other than our Jack Frost and then you can do whatever you want with it. This is just an idea I had but I suck at writing fanfiction so I put the idea here for someone else to write (but make sure to send it to me)