Route 30

Mr. Pokémon trades you an Exp. Share for the Red Scale from the Lake of Rage's red Gyarados, 2 tiles north and 5 east of his house's exit.

Mr. Pokémon hands you the Mystery Egg the first time you enter his house on Prof. Elm's errand.

Mr. Pokémon gives the Red Orb in his house when you visit after Prof. Oak hands you a Kanto starter, which Oak offers once you beat Red.