His presence serves as an Easter Egg.
Uncle Leo spends all of his time wandering the second floor of Muurine's house. He never exits the top floor so he has little interaction with anybody. The only way to see him is to go into the house and enter the second floor.
- Uncle Leo's name is a reference to the super mutant named Uncle Leo in Fallout 3, another game developed by Bethesda Softworks.