7. Batman Begins - How Thomas Wayne Met Alfred
Michael Caine likes to draw up a character biography for every role he plays, so when he accepted the role of Alfred he decided to draw on his own background. He revealed in an interview that Thomas Wayne met Alfred while visiting an SAS camp. Alfred had been wounded in combat and was unfit to fight, but instead of going back to civilian life he chose to head up the Sergeant’s mess instead, where he learned to perform all the duties of a butler.
The two men formed a friendship, and Wayne later hired him to become the family butler. Christopher Nolan liked this backstory so much he later incorporated Alfred’s background into The Dark Knight, where he recounts a story of a crazy thief in Burma.
This shared history explains why Thomas would entrust Bruce with the butler following his death, and why he’s able to knock out the occasional henchman if need be.