From Bulbapedia, the community-driven Pokémon encyclopedia.
Daybreak Contest under the Double Performance rule
Double Performance (Japanese: ダブルパフォーマンス Double Perfomance) is a rule used in Pokémon Contests. Contests under this rule are generally the same as any other Contest, with the only difference being the fact that Coordinators use two Pokémon in all rounds of the competition, unlike the Hoenn and Kanto Grand Festivals, which only had Double Battles in their last few rounds.
It was first mentioned in A Stand-Up Sit-Down!, when Zoey said the Hearthome City Contest and the Sinnoh Grand Festival would follow it. Because of this, Dawn had to find a pair to use. Zoey then showed her an example of an appeal using her Glameow and Shellos. The Double Performance rule was first seen in use in Dawn's Early Night! for the Hearthome City Contest, in which Dawn used her Piplup and Pachirisu. However, she was unsuccessful and lost in the Appeals Round.
Later on, it was announced in Unlocking the Red Chain of Events! that the Daybreak Contest would also be held under the Double Performance rule. Dawn participated in this Contest in Yes in Dee Dee, It's Dawn! and Playing the Performance Encore!. She was able to pass the Appeals Round this time with the help of her Piplup and Pachirisu. She eventually won the competition and earned her fifth Ribbon after defeating Ursula with her Cyndaquil and Mamoswine's Flame Ice combination.
The Sinnoh Grand Festival, which was held from Last Call — First Round! to A Grand Fight for Winning!, featured an Appeals Round in which Coordinators had to use two Pokémon. After that, they had to undergo several rounds Double Battles. In the end, only Dawn and Zoey were left to face off in the finals. Their battle ended with a combination of Zoey's Glameow's Thunderbolt and Zoey's Gallade's Psycho Cut versus a combination of Dawn's Piplup's Peck and Dawn's Togekiss's Sky Attack, with Zoey being the victor of the entire Grand Festival.