Unlike other characters prominently featured in the Sonic games, Froggy is not anthropomorphic and instead appears to be a giant version of a generic real-world tropical frog. Froggy's original and largest role occurs in Sonic Adventure where his isolated life alongside dimwitted fisherman Big the Cat is interrupted after he is possessed by the malevolent creature Chaos. After being possessed by Chaos, Froggy grows a tail, eats Big's Chaos Emerald and runs away from their home in the Mystic Ruins. Big follows closely behind Froggy, fishing him out of various pools in the world only for Froggy to run away again. Froggy is eventually captured by E-102 Gamma, a robot working for Dr. Eggman who is trying to collect all the Chaos Emeralds.
Froggy is brought onboard Eggman's ship, the "Egg Carrier", and is eventually absorbed into a highly evolved version of Chaos. The Emerald within Froggy provides Chaos extra power but Froggy is recovered from the being after it is defeated by Sonic. After Froggy is reunited with Big, the two are shown returning to a life of carefree fun in the jungle. According to Big, he and Froggy have been friends for years.
Another plot-driving role for Froggy occurred in Sonic Heroes where he was once again taken by Eggman and Big the Cat, Amy Rose, and Cream the Rabbit adventured across the world to recover him. Froggy has appeared as a cameo character in many other Sonic games, although eventually disappeared from the franchise as Big the Cat was phased out of it.