Mametchi serves as the primary mascot for the Tamagotchi franchise, debuting in the original 1996 virtual pet release and appearing consistently across subsequent media. He is recognized for his high intelligence, with an IQ of approximately 250, and his polite, serious demeanor, maintaining formal speech patterns even among close companions. Mametchi demonstrates persistence in his hobby of inventing, though his creations frequently malfunction or fail entirely. He exhibits notable weaknesses in artistic pursuits, particularly drawing and singing, often described as tone-deaf. Physical activity and academic study are among his preferred interests, and he maintains disciplined daily routines.

Physically, Mametchi typically appears light yellow with a wide, round head and narrow body. His most distinctive features include large black eyes and two prominent bumps on his head resembling fur-covered animal ears. Design revisions in 2004 introduced rosy pink cheeks alongside dark blue eyes and ears. An early localization attempt for North American markets briefly depicted him as female with a blue coloration and leaner proportions, though this interpretation was later abandoned in favor of maintaining his original Japanese design globally. Some media variations present him in pink or blue color schemes.

Within narrative contexts such as the "Let's Go! Tamagotchi" shorts, Mametchi engages in typical daily activities like school participation, relaxation periods, and community visits alongside companions Memetchi and Kuchipatchi. Specific episodes highlight his inventive endeavors, including creations intended to impress peers, and his involvement in competitive activities like sports tournaments against counterparts such as Kuromametchi. School-related responsibilities, gift selection for instructors, and participation in organized fan clubs also feature among his documented interactions.

His familial connections include identification within the Mame Family lineage, with Chantotchi established as his female counterpart. Mametchi's birthdate corresponds to the franchise's inception date, November 23. Relationship dynamics involve potential marriage outcomes with certain characters like Violetchi in virtual pet narratives, influencing subsequent generations. His parents, referenced as Mamametchi, appear in supporting media roles. Background narratives consistently position him as a benchmark character against whom other Tamagotchi characters are frequently compared, reinforcing his status as the franchise's central figure.