The Fat Lady guards the password and entry for the Gryffindor common room, and the password is changed regularly to prevent anyone not a Gryffindor from sneaking in. Each house has its own way of entry.
I purchased this from a wonderful seller on Etsy: Magicbimbo. She has many great Harry Potter ornaments she makes and sells!
I’ve also purchased the Three Brothers ornament, the Azkaban Prisoner Plaque, the Mirror of Erised, the Mermaid Window, and the Educational Decrees from her.