Pokémon : S5 | E16 – Bulbasaur… the Ambassador!

Ash and his friends are on their way up a hill when a couple of milk cans start to roll towards them. They break into a sprint until someone calls out to them, and soon they stop the runaway cans. The group helps load them back into the man's vehicle. He asks where they are headed, and upon hearing that they are going to Ecruteak City he offers to drive them part of the way.

They arrive at an airport, and their escort, Carter, says it will get them to the Moomoo Ranch near Ecruteak City. While they wait for their tickets, Ash calls Professor Oak's Laboratory. On the other side, however, are Mimey and Delia. Tracey and Professor Oak appear onscreen and then Oak explains that the many wild Pokémon that live in his lab’s sprawling gardens have recently had trouble. A group of migrating Hoppip, Skiploom and Jumpluff decided to stop at Oak’s gardens, but this ignited a territorial squabble with the resident Oddish line and then the Water-type Pokémon. Oak asks Ash if he could send over his Bulbasaur to act as the peacemaker, given its history with Melanie. Bulbasaur happily accepts the task, so Ash transfers it directly to the Professor. The call ends, and Oak greets Bulbasaur as it arrives.
(Source: Bulbapedia)