U2 was Yugi Mutou's Digital Pet in the Toei Yu-Gi-Oh! anime. It is based on U2 form the Yu-Gi-Oh! manga.
Yugi and Katsuya Jonouchi interacted their pets. Jonouchi's pet, Joe, initially bullied U2, but they became friends afterwards.
Kujirada linked his pet, Devil Master, with other Digital Pets and had it eat them, including Sumomo-chan and Joe. He tried to let it eat U2, but Hiroto Honda arrived, after spending three sleepless nights taking care of Super Strawberry, which he used to defeat Devil Master, saving U2.
Haiyama later attacked Yugi, causing Dark Yugi to emerge. Dark Yugi connected U2 to Haiyama's Digital Pet. Using the data it incorporated from its connection with Joe, U2 turned into a more powerful form and defeated Haiyama's pet.