In the anime
A feral boy freed the captured Kangaskhan with his boomerang, and led them in action against Team Rocket.
Later, a rich couple arrived in a helicopter and explained they were looking for their son, Tommy, who had been missing for five years. The family was flying over the Safari Zone when the father held their child outside the window of the plane to give him a better look and dropped him.
The couple showed Officer Jenny a picture of their boy, and she recognized him as Tomo - the feral boy who protects the Kangaskhan.
Brock tried to help an injured baby Kangaskhan and Tommy attacked Brock with his boomerang. Tommy's human parents try to explain who they are, but Tommy insists that the Kangaskhan have always been his real parents.
Tommy's father knocked him unconscious and the boy remembered his past.
Team Rocket tried to steal the Kangaskhan again with a giant robot, but Tommy's parents crashed their helicopter into the robot to destroy it.
Tommy's parents emerged from the rubble, however, and announced that they planned to live in the Safari Zone with Tommy and the Kangaskhan herd.
His Japanese voice actor is unknown and his English voice actor is Jimmy Zoppi.
In the manga
Electric Tale of Pikachu
Tommy also makes an appearance in the Electric Tale of Pikachu manga.
Pikachu had accidentally gotten separated from Ash. Pikachu met up with two abandoned Pokémon: Squirtle and Charmander. Pikachu had heard Ash talking about finding the Hidden Village. Squirlte and Charmander also sought the village.
Along the way, Tommy, a boy with a boomerang, greeted them. Tommy was able to speak Pokémon language and introduced them to his mother, a playful Kangaskhan. Kangkaskhan explained how she had found Tommy abandoned and raised him.
Kangaskhan and Tommy knew where the Hidden Village, the Pokémon Paradise, was located - and agreed to lead the three lost Pokémon there. After a while, they stumbled upon Meowth of Team Rocket. Meowth introduced them to Jessie and James and Tommy tried to ride around in Jessie's "pouch" (or possibly to drink milk from her breasts in the original version).
Jessie and James convinced them to take them along with them to the Hidden Village, acting like they wanted to live a quiet life in the mountains.
Everyone parted ways, and Kangaskhan and Tommy were still in the Hidden Village with Squirtle, the last Pikachu saw of them.
In the original version, Tommy seems to be obsessed with breasts.