Delibird gave Jessie and James two Poké Balls containing a Charizard and an Aggron. Excited at having two strong Pokémon, they decided to use them to attack the Pewter Gym and steal the Poké Balls in the Gym. When they entered, they challenged Brock and Ash to a Double Battle.
Using their Donphan and Steelix, the two friends tried to defeat Team Rocket's newly acquired Pokémon. However, the Aggron and Charizard were stronger and gained an early advantage. The battle was ended when Max discovered that the two Trainers were indeed Team Rocket in disguise. With the help of Forrest, Team Rocket were sent blasting off and Pewter Gym was safe.
At the end of the day, Delibird returned and took the two Pokémon back, as the Charizard and Aggron were originally intended for Cassidy and Butch, respectively. Before Team Rocket could question what it was doing, it was gone, and Aggron and Charizard haven't been seen since.
It is assumed Aggron was delivered to Butch successfully.