Pokémon : S5 | E37 – Wish Upon a Star Shape

On the night of a full moon, Ash and his friends gaze at the sky as their Pokémon play together. The group spots a shooting star, and they close their eyes to make a wish each. When they open their eyes again, Ash notices the shooting star is behaving strangely. It soars towards them, revealing itself to actually be a UFO, and shoots out an object which lands on Phanpy's back. Soon, the flying saucer crashes on a nearby mountain, which also catches the attention of the Pokémon Mystery Club.

Ash looks up the mysterious pink Pokémon on his Pokédex, and it turns out to be a Cleffa. Phanpy recovers from its shock and befriends Cleffa. Soon, Cleffa points towards the place where the flying saucer landed. Brock and the others notice Cleffa's concerns, and they decide to help Cleffa return to its friends. Team Rocket is also watching and decides to capture Cleffa. Just then, two people run up to Cleffa and start studying it, identifying themselves as Ken and Mary of the Pokémon Mystery Club, or PMC for short. They ask to take Cleffa, but Ash thinks they may be members of Team Rocket. Ken and Mary are instantly annoyed and call Team Rocket an awful organization. The Rocket trio reveals themselves in anger and recites their motto. The PMC is infuriated by their presence and reveals their machine. The machine shoots out a net, though Phanpy runs off with Cleffa on its back in time. Pikachu uses Thunderbolt on the PMC, creating smoke, and the group follows after Phanpy. While Ash and his friends head toward the mountain, Team Rocket cannot find Phanpy and Cleffa, so they use a divining stick to show which way they went. As they begin to head that way, PMC appears and shows off another machine that resembles a satellite; which soon reveals Cleffa's location. Then, they bring out another machine, which resembles a snowplow. It quickly catches up to Phanpy and Cleffa while they are at a cliff. Phanpy looks around for an escape plan. It resorts to knocking over a tree to use as a makeshift bridge and walks across it.
(Source: Bulbapedia)