As it is a man-made Pokémon designed to move around cyberspace, Porygon2 has been in use mainly via Blue's Pokédex as a surprise attack.
Porygon2 first made its appearance as a Porygon in A Tale of Ninetales where it was shown being obtained by Blue from the Celadon Game Corner; however, this Pokémon was disobedient and ran away from his new Trainer. After chasing it, Blue accidentally crashed into Red, causing a switch with both Trainers. Porygon was later used against Koga in the Silph Co. Building where it was used to defeat the Gym Leader along with Pika.
In The Primeape Directive, Porygon was used to defeat a group of rampaging Mankey and Primeape after using its ability to move through cyberspace to switch from Blue's Pokédex to Yellow's. It was later used to fight and defeat Agatha's Gengar with help from Koga.
Porygon first appeared in Claws on Porygon2 where it was revealed to have evolved into a Porygon2; it was used to fight Silver's Sneasel before they were interrupted by Entei.
Porygon2 made its first appearance in the FireRed & LeafGreen arc in Tower with Will when it was used to disable Trainer Tower AI "R" so that Blue and Green could rescue their family members. At first, it succeeded but not long after "R" came back online and trapped it with a Virtual Lock.