Pokémon Season 9 Episode 44

Ash trades in some of his old Pokémon and brings Bulbasaur, Charizard, and Squirtle back. They head up into the mountains for a little training and reminiscing of the past. After stopping yet another Pikachu stealing attempt from Team Rocket, Ash runs into Brandon who is impressed by the four Pokémon. Brandon declares a 4-on-4 battle this time so he can see the true strength of the four. Ash agrees and the next day the battle begins.