From Bulbapedia, the community-driven Pokémon encyclopedia.
The Wallace Cup (Japanese: ミクリカップ Mikuri Cup) is a tournament in the anime that is held in several places worldwide. It is hosted and judged by former Sootopolis Gym Leader and current Hoenn Champion, the Contest Master Wallace.
The Wallace Cup in Sinnoh was announced in Our Cup Runneth Over! on Sinnoh Now, where Dawn found out about it and became excited. Eventually, she, Ash, and Brock ran into Wallace himself, who was relaxing with his Milotic in a lake; Ash was convinced to enter the Contest with his Buizel, which he used in the three rounds he competed in before losing.
In Goodbye, Junior Cup - Hello Adventure!, Dawn announced she intended to compete in the Wallace Cup again, this time held in Johto.
The Wallace Cup is a special Pokémon Contest that is hosted at various locations throughout the world, and the most recent one was hosted at Lake Valor in the Sinnoh region, with the prize being the Aqua Ribbon, a Contest Ribbon that counts towards any region's Grand Festival, not merely that of the region it is won in. For this reason, Pokémon Coordinators migrated from all around the nation to compete in it.
The competition started in Staging a Heroes' Welcome! and ended in Strategy with a Smile!. Like all Sinnoh Pokémon Contests, Marian is the announcer. Jessadia, who was Jessie in disguise, also hosted the Wallace Cup with Marian.
May traveled all the way from Johto to compete in this Contest, but she lost to Dawn in the final round.
Each round is judged by a panel of four individuals. They include Raoul Contesta, Mr. Sukizo, a Nurse Joy from the Sinnoh region and the Contest Master, Wallace.
Just like regular Contests, the first round is the appeals stage. Coordinators have their Pokémon perform various moves in order to impress the judges. Once everyone had appealed, the 16 top scoring Coordinators progressed to the second round.
The second stage marks the beginning of the Wallace Cup's battle rounds and shows how skilled Coordinators and their Pokémon are when put into battle. All Coordinators are matched-up randomly by computer up to the semi-finals, which is the last round that computer will choose a random match-up. Coordinators who ran out of points, had their Pokémon knocked out or had the least amount of points once the time ran out were eliminated from the Wallace Cup.
Dawn, the winner, with the Aqua Ribbon