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 could be a reference to the super mutant named Uncle Leo in Fallout 3, another game developed by Bethesda. Although, because the Shivering Isles DLC was released in 2007, and Fallout 3 was released in 2008, it's possible the reverse is true.
- Uncle Leo reappears in The Elder Scrolls Online as a boss in the Mages Guild quest Chateau of the Ravenous Rodent. There he appears as a Flesh Atronach rather than a Zombie.