Remus remembers those mirrors. The two of them had thought themselves so clever when they figured it out, experimenting and running trials in the dormitory. Remus had offered to do some research and help, but this was something they had wanted to do on their own—Peter had rolled his eyes and told Remus that they just didn’t want to share, and if Remus had helped they would have felt obligated. "This is just a "best friends" thing," Peter had said, lifting his fingers to make air quotes around the words. "Us mere dorm mates don’t get to be part."