Barnacle Boy is depicted as being the undercredited and underappreciated younger sidekick of Mermaid Man. Grumpy and slightly ill-tempered, Barnacle Boy is notable for his brooding, moody disposition and exasperation with his partner's absentminded behavior as a result of old age, and even into his golden years, Barnacle Boy is still treated in a juvenile fashion, coddled in an infantile way.