Ash sends Bulbasaur to Professor Oak's Lab to act as an ambassador between two groups of Grass Pokémon and one group of Water Pokémon, Ash's Bulbasaur learns Dig, Ash and Bulbasaur agree that Bulbasaur should remain at Oak's lab on a permanent basis.
After winning the Mineral Badge from Jasmine, Ash and co. decide to head to the next Gym, located at Mahogany Town. To get there, they have to go through Ecruteak City again. Sometime later, Ash calls Professor Oak and is surprised to see his mom at the lab. Professor Oak and Tracey then come in and explain the situation:
A few days ago some Hoppip, Skiploom and Jumpluff landed in an area occupied by some Oddish, Gloom, Vileplume and Bellossom and begin to fight over it. Then some Water Pokémon join in the dispute.
To solve the problem, Professor Oak requests Ash send in Bulbasaur to straighten things out. What kind of solution will Bulbasaur come up with?
With Bulbasaur staying at Oak's lab, Pikachu is the only Pokémon that remains on Ash's Team throughout this and every other Pokémon series.