Nonnyis a brainy, cautious, and overly calm male guppy. He's more likely to comment on the action than get swept up in it, and he often uses an advanced vocabulary for his age. Physical activities make Nonny a little unsure of himself, as he'd rather define "basketball" than play it.
His willingness to keep trying, combined with encouragement from his friends, often leads him to triumph in the end. Nonny loves to read books, and has been seen doing this in several episodes. His nickname is Nonners, although nobody calls him that but Deema. His original nickname is "Mr. Cautious."
Nonny has peach skin, orange hair, and green eyes. He wears blue glasses, which resemble scuba goggles. His tail is light green with dark green stripes. His ears are slightly larger than the other guppies'. He is thinner than them as well. Because of his thin stature, it gives him the illusion of having unusually large hands.
Nonny has been shown playing instruments in multiple songs. For example, in "Puppy Love!", he was shown playing a tamborine, and in "The Puppy And The Ring", he played the guitar and piano.
Nonny has been shown to be a background dancer in many episodes, however his dance skills have been shown to not be as good as the others. An example of this is in "The Wizard of Oz-tralia!", when he was dancing with the others to the Dingo song. Nonny was also seen doing the robot in the song Check It Out!
Nonny's friendship with Gil is pretty normal; they are really good friends. In the episode Fishketball!, Gil helped Nonny learn how to catch a ball and at the end of the game, he then thanked him for his help.
Despite the fact that they don't hang out as much, Goby considers Nonny as his friend. The two love to narrate the stories their friends play in during recess, and have even acted in a story together in The Amusement Parking Lot!.
Nonny has appeared in every episode of the series.