Although overworked and underappreciated, and bitter towards the player because of that, Doc Church is always professional. He used to be a medic at Paradise Falls until he moved to Megaton. At that point, the town had been without a doctor for years. Doc Church was born in 2223.
Doc Church can be found at the Megaton clinic at any given time during the day.
Regardless of player's health when initiating dialogue with him, he continues to make remarks that you are in good health and should not bother him. Even coming in with deadly radiation poisoning will still have him remark about how you look fine.
Doc Church is a very light sleeper and will wake if you come into his room, even if you are sneaking.