He is a small light purple slug with a light green underside. He has yellow eyes, and black pupils as well.
At the end of the episode, the elder starfish finds a coffee stain revealing Gary to be Sluggo's son, and the true and rightful king of Bikini Bottom.
- Given that the right to become King was passed to Gary, rather than Patrick, this means that Sluggo is the older brother of Herb.
- Concept art from a scrapped storyline of The SpongeBob Movie: Sponge on the Run showcase that Gary originated from another planet with very different parents. It's unknown if Gary's father on the concept art is Sluggo or another character.