The Psyduck Stops Here! (Japanese: コダックの通せんぼ！The Koduck Roadblock!) is the 87th episode of the Diamond & Pearl series, and the 553rd episode of the Pokémon anime. It first aired in Japan on July 24, 2008, and in the United States on December 27, 2008.
Our heroes are on the path to Celestic Town, but the road runs through a narrow pass that's blocked by three irritable Psyduck. If Ash and his friends take a detour, they'll miss the Celestic Town Contest, but the Psyduck's Psychic-type attacks repel anyone who tries to get through. Ash and his friends do their best to force the Psyduck out of the way, but none of their Pokémon can get in an effective attack. The Psyduck aren't interested in negotiating with Piplup, either! Team Rocket pops in to try and recruit the Psyduck for Team Rocket, but they too are blasted out of the way.
There must be a reason for the Psyduck's behavior, so Ash hitches a risky ride on Gliscor and flies ahead to scout the path. While Ash is on his mission, Brock sings and dances to distract the Psyduck. Ash and Gliscor crash-land near a pond filled with more Psyduck, nursing their Eggs—that's why the Psyduck in the pass are on guard! Ash returns and reports to the others just before Team Rocket returns in an attempt to steal the Psyduck. Ash and his friends team up with the Psyduck to beat Team Rocket, earning some trust from the Psyduck.
A Psyduck messenger summons the Psyduck in the pass, and everyone runs to the pond in time to see the Psyduck Eggs hatch. As Brock dishes up Pokémon food to help earn the Psyduck's trust, he wonders why the Psyduck are in a small pond instead of nearby Lake Psyduck. When our heroes investigate Lake Psyduck, they're attacked by Muk that have taken over the lake! Ash and his friends send the Muk flying into another pond, which just happens to be inhabited by female Muk. The Muk happily pair up and the Psyduck families return to Lake Psyduck, so the road ahead is clear for the trip to Celestic Town!
Ash and his friends are traveling through a valley on the way to Dawn's next Contest in Celestic Town. They encounter three Psyduck in the middle of the road. After confirming with Brock that the Pokémon are Psyduck, Dawn scans them with her Pokédex. As they walk closer to them the Psyduck's eyes glow pink, surrounding the trio with pink as well and lifting them up with Psychic. Ash, Dawn and Brock sit down to come up with a plan to get around them. When it seems like there's no other choice but to use force, Ash sends out Turtwig who attacks with Razor Leaf and Bite, but the three Psyduck are too powerful and Ash calls Turtwig back. Next up is Piplup who uses Whirlpool but is defeated by the Psyduck, who use Psychic to reflect Whirlpool back to Piplup. Brock sends out Croagunk who uses Poison Sting, but he too is defeated. Chimchar also comes out, uses Dig (as Ash thinks Psychic won't reach underground), gets lifted out of the hole by the Psyduck, smashed into the ground, and defeated.
Team Rocket appears and do their motto. They haughtily state that they can do a better job of getting the Psyduck out of the way than the twerps can. Meowth walks up to the Psyduck and attempts to bargain with them. However it backfires and Team Rocket is sent blasting off by Psychic to the top of the valley. Brock's Happiny comes out and uses Pound while the Psyduck use Psychic on Happiny, crashing her to the ground. Happiny gets angry and starts lifting up a gigantic boulder to throw onto the Psyduck, but she loses her balance and swerves around while Ash, Dawn, and Brock try not to get hit. Eventually, Happiny crashes and breaks the boulder, fainting. Dawn's Swinub is sent out, but gets defeated as well. They then come up with a plan for Staravia and Gliscor to fly around with Ash while Dawn and Brock distract the Psyduck. Brock begins to perform Brock's Paradise while Ash and Gliscor take off. Gliscor flies into the wall a little farther down the valley. Ash sees a few mother Psyduck holding Eggs, and realizes that the Psyduck are protecting their babies.
Back with Brock, he is still performing the song but is getting tired. Ash reappears with Gliscor and lands. He explains to Brock and Dawn that the three Psyduck are just protecting their babies. Team Rocket reappears again in their Meowth Balloon and perform their motto again. Ash, Brock, and Dawn send out Staravia, Croagunk and Buneary respectively to battle Team Rocket. Chimchar also comes out to fight Carnivine and Yanmega. Team Rocket blasts off.
They return to the lake in time to see the Eggs hatch. They wonder why they are not at their lake, when three Muk rise up from the water. Dawn scans the Muk with her Pokédex. They send the Muk out of this lake and back into their original lake where they meet three other Muk and fall in love. The Psyduck hop back to the lake as Ash, Dawn and Brock continue their journey to Celestic Town.
For the first time, this song is left intact in the dub.
After he is knocked out, Dawn returns Piplup to his Poké Ball for the first time since Pruning a Passel of Pals!, in which the episode number is a reversal of this episode. Once he was returned, he didn't reappear for the rest of the episode.