Pokemon Season 11 - Episode 521 – Nosing ‘Round the Mountain

Ash battles Alan, a trainer that wants his Nosepass to evolve into a Probopass, but it can only evolve if it levels up in Mt. Coronet. When it does, Team Rocket brainwashes it and now Ash & Co. have to get it back. 

Pokemon Season 11 - Episode 520 – Bibarel Gnaws Best!

Ash's group encounters a Pokémon Breeder working on the construction of a stone bridge. The woman is arguing with the bridge's designer because of their Pokémon assistant Bibarel's refusal to work. After the stone cutter returns, Bibarel begins to construct the bridge, with help from the Gang. 

Pokemon Season 11 - Episode 519 – The Keystone Pops!

After Ash's Buizel destroys the Hallowed Tower, a Spiritomb is unleashed and attacks Ash, Dawn, Brock and a nearby village. Then Jessie tells it that Ash is a descendant of the Aura Guardian that coincidentally has a Pikachu, that sealed it away. So Ash sets out to stop the Spiritomb and with Pikachu's help, they seal it away in the Hallowed Tower.