Pokémon the Series: Sun & Moon Episode 21: One Journey Ends, Another Begins...
Episode 21 of 146 of Pokémon the Series: Sun & Moon, aired April 6, 2017, 25 minutes. Available with English subtitles and dub where released.
Episode summary
After stealing his groceries again, the wild Litten comes to Ash for help when its friend Stoutland starts to have trouble breathing. Ash struggles to get it to the Pokémon Center...but Stoutland is old, and there’s not much Nurse Joy can do.