Brodie debuted in the episode Unfair Weather Friends, disguised as Millie, a scientist at the Weather Institute who was supposed to be collecting data on Groudon. Team Aqua tried to steal the data directly, unaware Millie was really Brodie. When Shelly threatened to harm Bart and the other scientists at the Institute, Brodie revealed himself as a Magma agent and escaped with the information the Institute had gathered on the legendary Pokémon.
Brodie also appeared in The Ribbon Cup Caper. He disguised himself as various people, including Officer Jenny, in order to steal the Ribbon Cup for the Hoenn Grand Festival. When confronted by the real Officer Jenny, Brodie willingly gave up the Ribbon Cup because "it wasn't valuable enough" and flew away once again. He hasn't been seen since.
Brodie was a member of Team Magma (or mercenary on their payroll) before its dissolution, after which he became known as "Brodie The Phantom Thief". He is also known as "The Man of a Thousand Faces," having perfected the art of disguising himself in order to get his goals accomplished.