Macca the Gator is a TV character in the world of the game, tied to the Goodtime State. The Ultimate Edition includes Goodtime Gear: clothes and accessories that refer back to that series.
Macca is not an announced protagonist. The character is an example of how the game pulls local celebrities and brands into the world.
The official Ultimate Edition text calls Goodtime Gear 'a capsule collection of apparel and accessories inspired by the Goodtime State's hit TV show character, Macca the Gator.' The Goodtime State is one of the nicknames Rockstar uses for Leonida, which makes Macca a piece of local pop culture inside the game.