It's the punchline to a meme. This is one example: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRgeiEhXUMDBIeGK5mJSMSLxrwF7GJb-8HwnA&s https://encrypte

It's the punchline to a meme. This is one example: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRgeiEhXUMDBIeGK5mJSMSLxrwF7GJb-8HwnA&s https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRgeiEh... I don't think it's quite the same as calling yourself or someone else a "friend of Dorothy". People who say they are into trains usually precisely mean they are into trains.