Route 30

After you beat Red and take a Kanto starter from Prof. Oak, Mr. Pokémon gives you the Blue Orb as you next enter his house.

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.