Uncle Leo

 is a friendly, wandering super mutant whom you can meet in a random encounter.

Background
He is an exile of sorts from the super mutants; he ran away before he could be killed, because he was showing peace/dissent among his kind. Since then, he has roamed the Capital Wasteland. He frequently refers to the Lone Wanderer as either "Little Brother" or "Little Sister", depending on the PC's gender.

Uncle Leo is unarmed and wears only a pair of shorts. He is non-aggressive and will never initiate combat (even against Yao Guai or Deathclaws), but he will defend himself if attacked.

Location
Uncle Leo is a random encounter and might be found in any of those locations.

Interactions with the player character
When speaking to Uncle Leo, he will be surprised that you haven't shot at him yet. As long as you're nice to him, you can get more than information. When the option comes in at the top to tell him to give you his goods (essentially "robbing" him), he gladly imparts a suit of Dirty Pre-War Businesswear to you as a gift, wishing he could give more.

Asking him what he meant when he said "before I became this" causes him to tell the player that Super Mutants are not born but are made by other super mutants in a cold dark place. He mentions that they use the captives that they take to make more of themselves, but he either doesn't know or cannot explain how this is done.

Uncle Leo can be encountered a second time. He will tell you that after your first encounter with him he fell into a dark cave while climbing a hill and hurt his leg. The cave turned out to be an old basement in which there were stacks of purified water. He tells you that after he got out of the basement he has been hunted by a group of "bleeders" (as super mutants refer to humans) and that he was forced to abandon the water he was carrying. As during the first encounter, he will offer you another suit of Dirty Pre-War Businesswear, wishing he could give you more.

As a follower
He attacks any enemies that attack the player character. However, he has only moderate morale, and will drop his weapon and run away if he takes too much damage.

He is initially unarmed, but like all NPCs will try to acquire weapons from the environment if brought into combat. His health is on par with that of a Super Mutant Master. He cannot heal damage or be given/reverse-pickpocketed stimpacks, so repeated enemy encounters will eventually mean the death of him.

Attacking Uncle Leo causes him to switch to hostile. However, once the game finishes running the attack animation, Uncle Leo returns to friendly, even when the player is obviously his tormentor. Attacking and/or killing him causes no change in karma.

Appearances
Uncle Leo appears only in Fallout 3.

Behind the scenes

 * Uncle Leo's dialogue when you try to rob him, where he tells you the clothes are a gift and he wishes he could give you the "wonderful moon", comes from the following Zen Buddhist koan:

''Ryokan, a Zen master, lived the simplest kind of life in a little hut at the foot of a mountain. One evening a thief visited the hut only to discover there was nothing to steal.  Ryokan returned and caught him. “You have come a long way to visit me,” he told the prowler, “and you should not return empty-handed. Please take my clothes as a gift.”  The thief was bewildered. He took the clothes and slunk away.'' ''Ryoken sat naked, watching the moon. “Poor fellow,” he mused, “I wish I could have given him this beautiful moon.”''