Pokémon : S3 | E21 – Foul Weather Friends

While traveling along the road to Azalea Town, Ash and his friends notice many Grass-type Pokémon, including a Pokémon hopping along the path, which Brock identifies as a Hoppip. Suddenly, a breeze picks up and lifts the Hoppip into the air, and the trio pursues it. Just then, a girl appears and catches Hoppip in a large butterfly net. As she sets the net down, another Hoppip floats down and lands on her head. The trio catches up with her, and the girl introduces herself as Mariah. She explains that the two Hoppip belong to her along with five others, which she uses to predict the weather. Leading the group outside, she predicts that the wind will pick up because the Hoppip have all clustered together. Sure enough, a breeze arrives and sends two of the Hoppip soaring away, only to be caught by the fence. Mariah announces that such a breeze only rates a two on the Hoppip Scale, as it was only strong enough to lift two Hoppip.

Mariah announces her plans to do more research on the relationship between Hoppip behavior and the weather in order to help meteorologists to make long-range predictions. Once more, the Hoppip group together just before another breeze lifts all but one of them away. The last Hoppip quickly runs after the others, climbing a rock and jumping off in an effort to fly like them, but it fails. As Misty aids it and cleans it up, Hoppip's pink color washes off and reveals the Pokémon to be an Oddish. Mariah explains that the Oddish is a Pokémon from the neighborhood that spends so much time with her Pokémon that it wants to be just like them. As they speak, Oddish climbs up a section of the wire netting and jumps off, this time finding a softer landing in a pile of hay. Meanwhile, Team Rocket is watching from a distance. Upon seeing the Hoppip, Meowth suggests stealing them and using them for a delivery service business, but Jessie and James dismiss that idea and suggest stealing them for the Boss.
(Source: Bulbapedia)