Yu-Gi-Oh! Duel 21: "Digital Pet Duel"
Yu-Gi-Oh! (Toei) episode 7: "The Underhanded Digital Pet Rebellion"
Jonouchi connected Joe with Yugi's pet U2 for a data exchange. As Digital pets commonly took after their owner, Joe began to bully U2, like how Jonouchi used to bully Yugi. The 2 pets became friends afterwards.
Jonouchi left Joe unattended while he left the classroom. During this time Kujirada fed Joe to his own pet.
When Kurirada tried to feed U2 to his pet, using the data it incorporated from its data exchange with Joe, U2 became more powerful and was able to defeat Kujirada's pet.
Eager to win a trip to Australia in an upcoming tournament, Jonouchi trained Joe hard. He continued to train him during school hours, rather than turn the Digital Pet off.
Jonouchi connected Joe with Yugi's pet U2 for a data exchange. As Digital Pets commonly took after their owners, Joe began to bully U2, like how Jonouchi used to bully Yugi. The 2 pets became friends afterwards.
After Kujirada got his pet, Devil Master, to eat Anzu's pet Peachy, Jonouchi connected Joe to Devil Master to battle. Joe initially caught Devil Master with a sneak attack, but was ultimitely eaten too. Honda then avenged the two of them by having Super Strawberry beat Devil Master.