Mametchi is a character from Tamagotchi, which is a chain of egg-shaped virtual pet toys produced by Bandai that have since established a franchise spanning over 20 years, including adaptions to other media such as video games, merchandise, and anime. On most Tamagotchi releases, Mametchi is the result of a Tamagotchi with the best possible care, being portrayed as very intelligent with an IQ of 250 and exceptional manners. Mametchi was initially one of several faces, but eventually became the mascot of the Tamagotchi franchise as a whole.
Mario Kart Arcade GP 2
Mametchi's first (and currently only) appearance in the Mario franchise is in Mario Kart Arcade GP 2, where he is a playable guest character presumably to coincide with Bandai's then-recent merger with Namco. He is categorized as an Easy-Control character, sharing stats with Ms. Pac-Man and Toad. His special items are Bagubagutchi, Mame Block, Chibi Syrup, Mame Drink, and Giant Pencil, and his voice clips imitate the beeping sound effect heard in Tamagotchi virtual pets.
As with the other characters, in addition to a standard kart, Mametchi gets a special vehicle that slightly reduces acceleration in exchange for increased speed. Mametchi's special vehicle loosely resembles a Tamagotchi virtual pet that is pulled by a wheeled mechanical Tamagotchi wearing a Kasa.