Incidental 13 is a light green fish. He often makes cameo appearances. He is married to a purple female fish (Incidental 12). In "Hall Monitor," they are shown eating a dish called seaweed medley in their house.
He is a light green colored fish who has olive green fins and light yellow eyes. He wears dark blue shorts with a white flower design.
In "Hall Monitor," he and Vera are first seen together as a couple and they are eating a meal together. In "The Great Snail Race," he is the referee for the race and shows up when the race begins and ends. His character is mostly quiet, but not completely silent.