He is a fictional character, who appears rarely in GTA 5 who is well known to the Banana Bus crew by his red light saber-like glow stick in which he swings it around while standing there. He hasn't been officially been called Darth Little D*** until his second appearance.
Darth Little D*** is a unknown person that Vanoss and Delirious found when they were traveling around in a GTA 5 Map. Darth Little D*** was first seen when Delirious found him and told his friends to come see him at which they see Darth Little D*** waving his glow stick until he was scared by Wildcat which made him drop his glow stick and ran off.
He wasn't seen again until Vanoss and Delirious stumbled upon him when getting more trash for their company. When they saw him, they tried to provoke him in order to fight. They were able to do it but a random guy ran and punched Delirious. Thinking he was a Star Wars fan, Delirious manages to beat him up and Vanoss did a two hit combo knocking out Darth Little D***.