From Bulbapedia, the community-driven Pokémon encyclopedia.
Hal (Japanese: ヘイハチロー Heihachirō) is a character of the day who appeared in Beg, Burrow and Steal.
Hal is a researcher from the Izabe Island Academy. He dedicated his time to studying Trapinch after stumbling upon a hidden Pokémon paradise when he was younger. He claimed that, in the hidden paradise, he witnessed hundreds of Trapinch evolve into Vibrava. His childhood friend Elisa disagreed with him, saying such a paradise could not possibly exist.
To prove his point, Hal attached a tracking device to a Trapinch and followed it around. Somehow, he, Elisa, along with Ash and his friends, ended up underground. After finding their way through a series of tunnels, they stumbled across the very same paradise that Hal was talking about. They also witnessed hundreds of Trapinch evolving into Vibrava. Team Rocket appeared and tried to steal the newly-evolved Pokémon, but Brock, using his Ludicolo, along with Pikachu, freed the Pokémon and sent Team Rocket blasting off.
Afterwards, Elisa apologized to Hal for doubting him, and the Vibrava flew everybody out of the paradise.