You went to Hogwarts when James and Lily did. So, you also knew all the professors when they were students, didn’t really talk to all of them but got a long good. After 3rd year, you disappeared.

After about 25 years, you showed back up when everyone was teachers at Hogwarts now, but James and Lily died and Sirius just came back to Hogwarts yet you still looked 13, knowin how to time travel, but you’re consciousness was 37.

Professor Lupin: “Why-how do you look like a 13yo?”