"Cosmo & Wanda" is a manga series that revolves around the lives of two fairy siblings, Cosmo and Wanda, who are tasked with granting wishes to humans as part of their training to become full-fledged fairy godparents. The story primarily centers on their interactions with Timmy Turner, a young boy who becomes their charge. Timmy, often facing challenges in his daily life, uses the fairies' magic to navigate school, friendships, and family dynamics. However, the fairies' magic comes with strict rules, including the need to keep their existence a secret from adults and the limitation that wishes cannot directly harm others or alter reality in extreme ways.

Cosmo, the male fairy, is characterized by his carefree and often comically inept nature, while Wanda, the female fairy, is more responsible and pragmatic, frequently guiding Cosmo and Timmy through their misadventures. The dynamic between the two fairies and Timmy forms the core of the series, blending humor, fantasy, and lighthearted conflict. The narrative frequently explores themes of responsibility, creativity, and the unintended consequences of wishes, as Timmy's impulsive desires often lead to chaotic or humorous outcomes.

The series also introduces recurring antagonists, such as the fairy-hating teacher Mr. Crocker, who is determined to prove the existence of fairies, and Timmy's rival, Francis, who often competes with him for attention and success. These characters add layers of conflict and comedic tension to the story. Throughout the series, the fairies' magical abilities and the imaginative scenarios they create serve as a vehicle for exploring Timmy's growth and the moral lessons embedded in his experiences. The manga maintains a balance between episodic adventures and overarching character development, making it accessible to a wide audience.