Pokémon : S5 | E34 – Same Old Song and Dance

Ash and his friends are travelling through a forest en route to Blackthorn City. As Ash gets hungry, Brock reads his guidebook and announces there is a town up ahead. This invigorates Ash and he starts running ahead. Unbeknownst to Ash and the others, Jigglypuff appears behind them. When they reach the town, Togepi runs off and meets a young girl named Brittany, who is practicing with her twin Igglybuff. Brittany introduces her two Igglybuff, nicknamed Gigglybiff and Gigglybuff, and explains that they star in her own musical variety television program called "Brittany"; it is her very first concert, which will be recorded live. She plays her CD player to begin a practice performance, with Ash and the others watching on. Meanwhile, Team Rocket spies on them, and Jessie daydreams of having her own show with the Igglybuff.

Jigglypuff suddenly shows up and begins to sing, but Ash snatches its microphone and stashes it in his backpack. Brock offers Jigglypuff some Pokémon food, which it gratefully enjoys. Brittany invites Ash and his friends to lunch. Upon hearing the compliments the two Igglybuff received, Jigglypuff becomes jealous of them, so she bullies them when Ash and the others aren't looking, kicking them and taking their identical headbands off. When Misty stumbles upon this, Jigglypuff claims the wind blew them away. After placing the headbands back, Jigglypuff nudges Misty's leg and is also invited to Brittany's concert.
(Source: Bulbapedia)