A relaxing day at the beach, fun in the sun, and a whole horde of Onix! Just as Ash and co. are spending their time to have fun and start their Expedition on Onix Island after they arrive here turns out to be a quest for survival as they try to avoid one Onix attack after another. The worst part is Iris, Dawn and Axew are separated for the group when they ran away in opposite directions trying to get out of the cave. Will they find the guys again and get out of here? Yes. And will Dawn's Piplup and Ash's Oshawott ever get along instead of fighting over for Meloetta since she comes along? Yes.
Piplup and Oshawott did work together to keep those Onixes away and get along (sort of,) once but in the end they're rivals over Meloetta again.
Who's that Pokemon?: Onix (US).
Dawn and Iris agreeing on everything is a refrence since the anime is practiclly the same but with different Pokemon and regions since gen 4