Sherlock: A psycho with a gun shot you in the shoulder while you were working on a case with your dad.
John: You twisted your ankle while playing football (Soccer) in gym class.
Mycroft: You accidentally cut your finger while you were chopping up some carrots in the kitchen.
Lestrade: You were walking down the hall with (Friend's name), Sherlock's daughter, and (Friend's name), John's daughter, at school when someone opened their locker and accidentally hit you in the face. The person who opened their locker wouldn't stop apologizing for hitting you in the race.
Moriarty: One Moriarty's men accidentally shot you in the arm while you were helping him fix his gun.
