Happy is a fictional character from the manga and anime series Fairy Tail. He is a small, anthropomorphic blue cat who belongs to a magical race known as Exceeds. Born from an egg that was discovered and hatched by the fire dragon slayer Natsu Dragneel six years before the main story begins, Happy was named for the joy his birth brought to the wizards of the Fairy Tail guild, symbolizing a bluebird of happiness.

As a member of the Fairy Tail guild, Happy serves as the closest companion and partner to Natsu Dragneel, and the pair are nearly inseparable. His primary magical ability, called Aera, allows him to grow white, feathered wings on his back and fly. This skill is crucial to his team, as he can carry people through the air, and uniquely, carrying Natsu does not trigger the dragon slayer's severe motion sickness, as Natsu does not consider Happy a simple mode of transportation. Despite his small size, he is shown to be capable of carrying multiple people at once.

Happy's personality is characterized by his cheerful, sardonic, and mischievous nature. He frequently teases his friend Lucy Heartfilia, poking fun at her weight, her romantic prospects, and walking into her apartment uninvited. His speech is punctuated by his signature catchphrase, "Aye!". He has an immense and well-documented love for fish. While often providing comic relief, Happy is also deeply loyal and brave. He possesses a significant amount of knowledge about the magical world and can offer simple, clever solutions to complex problems when the situation demands it. He emulates many of Natsu's actions and shares his fierce loyalty to his guild and friends, consistently placing himself in danger to support them. He also develops a strong, persistent romantic interest in Carla, a female Exceed who initially rejects his advances but eventually comes to respect and care for him.

Happy's background is explored during the Edolas arc, where it is revealed that he and Carla were sent from the parallel world of Edolas as unborn children in eggs. They were originally given a secret directive to kill Dragon Slayers like Natsu, but this mission is later revealed to be a cover story for an evacuation plan to save the Exceed race from the destruction of their kingdom. Learning this truth causes Happy great guilt, but Natsu's unwavering trust and friendship reaffirm their bond.

Throughout the story, Happy evolves from a simple mascot and mode of transport into a genuine hero. He plays an active role in key battles, such as destroying a powerful Lacrima to save the guild, destroying the power source of the Grimoire Heart guild with Carla, and even sacrificing himself to stop a massive explosion by carrying an enemy into the sky. He is instrumental in the final battle against the dragon Acnologia, and stands by Natsu when the truth of his nature as a demon is revealed, tearfully declaring that his friendship is unchanged. His key relationships include viewing Lisanna Strauss as a mother figure and sharing a friendly rivalry with fellow Exceeds Lector and Frosch from the Sabertooth guild.