Yanappu is Dent's best and only Pokémon, it made its first appearance in BW005 where he showed it to Ash who scanned it on his Pokédex, before standing next to Dent whilst he judged Ash's gym battle.
Yanappu was Ash's third and final Pokémon to face in his gym battle, Ash sent out Mijumaru. It was scared of Yanappu at first, but with some encouragement from Ash and Pikachu, it decided to battle. However, Yanappu dodged all of its attacks with ease and hit Mijumaru quite hard with Bullet Seed and Bite. After Mijumaru finally hit a midair Yanappu with Water Gun, Yanappu started charging Solarbeam, which petrified Mijumaru with fear.
It is set to appear in BW006.