Psyduck is a yellow Pokémon resembling a duck or a bipedal platypus. On top of its head are three thick strands of black hair, and it has a wide, flat cream-colored beak. Psyduck's eyes seem vacant and have tiny pupils. Its legs and tail are stubby, and it has cream-colored webbed feet. There are three claws on each of its hands.
Psyduck is constantly stunned by its headache and is unable to think very clearly. It usually stands immobile, trying to calm its headache. However, when its headache becomes too severe, Psyduck releases tension in the form of strong psychic powers. The use of these powers produces brain waves identical to those seen in sleepers, and the Pokémon is unable to recall these episodes. Psyduck lives in freshwater lakes and small ponds, but can be seen in rivers in tropical areas as shown in Pokémon Snap.
Psyduck debuted in Hypno's Naptime, where it was accidentally caught by Misty. Despite being generally shown as dimwitted and oblivious, when its headache gets bad enough, it has been shown to use phenomenally powerful Psychic-type moves, which far exceed its normal ability.
In Bye Bye Psyduck, Marina owns a Psyduck. It wasn't as dopey as the Psyduck Misty had, and even proved itself to be rather strong in battle, managing to defeat Staryu. However, it lost against a wild Golduck that Misty used under the belief that her Psyduck had evolved into it.
In Mewtwo Strikes Back, a Psyduck was cloned from Misty's Psyduck. It then participated in the battle between the original Pokémon and the cloned Pokémon. Psyduck reappeared in Mewtwo Returns.
In Sitting Psyduck, Emily had a Psyduck that persistently escaped from her mansion because it didn't like the lavish life she gave it.
In The Psyduck Stops Here!, eleven Psyduck (three newly hatched) lived by a pond. Three of the Psyduck were blocking the path that Ash and his friends needed to pass on their way to Celestic Town. Ash and friends later discovered that they were living by the pond because nearby Lake Psyduck had been invaded by a trio of Muk. Ash and friends later evicted the Muk and allowed the Psyduck to live by Lake Psyduck so that the Psyduck's road blocking days can come to an end.
A Trainer's Psyduck using a scarf, appeared in Memories of a Warming Kindness!. In the past, it helped Chrysa overcome her depression, after she lost her conference papers. This led her to have an obsession with Psyduck merchandise.
Two Psyduck appeared in The Sinnoh Iceberg Race!, with one under the ownership of a Trainer and the other being wild. The wild Psyduck retrieved Lauren's glasses, implying it will join her team just as her Piplup and Croagunk did.
Psyduck debuted in Sigh for Psyduck, where it was brought back to life by Koga's Gastly in the Pokémon Tower. It first appeared to Red like a normal Psyduck, until it attempted an assault on him, during which its eyeballs suddenly sunk into its eye sockets and some skin fell off, revealing its bones. Since it was just a mindless undead Pokémon, it was easily destroyed by Red's Saur's Vine Whip attack.
A herd of Psyduck appeared in Suffering Psyduck, where they were blocking the route to Celestic Town. However, included among them were Psyduck belonging to Trainers, and this was all a ruse by Team Galactic, which Cynthia catches on to shortly after calming them.
In Pokémon Scarlet and Violet, Psyduck is programmed to learn Simple Beam through breeding, but no Pokémon in those games can learn Simple Beam, making the move unobtainable until Pokémon HOME was updated. It shares this trait with Spoink.