To Catch a Rotom! (Japanese: ロトムVSオーキド博士！Rotom VS Dr. Okido!) is the 128th episode of Pokémon the Series: Black & White, and the 785th episode of the Pokémon anime. It first aired in Japan on May 30, 2013 and in the United States on August 31, 2013.
As our heroes continue their tour of the Decolore Islands, their next stop is Torom Island, where they meet up with none other than Professor Oak! He’s come to catch a Rotom as part of a research paper he’s writing about the unusual Pokémon’s various form changes, triggered by entering certain kinds of electric devices. As he’s telling Ash, Iris, and Cilan all about Rotom and what it can do, the lights flicker and then go out. Nurse Joy explains that the Rotom are drawn to the tasty electricity from the island’s power grid, so lunchtime blackouts are a common occurrence.
To combat this nuisance, the locals have created an electricity playground for the Rotom, with lots of devices for them to explore! It seems a likely spot to catch a Rotom, so our heroes and Professor Oak head there at once. They spot three Rotom traveling down the power lines, and Pikachu uses Thunderbolt to lure them in closer. The three seem to enjoy the taste of Pikachu’s electricity, but when Cilan’s Stunfisk tries to join in, they react with disgust. Emolga’s electricity is a big hit, though—at least until the three Rotom are distracted by a surge of electricity from somewhere else.
It’s Team Rocket! They’ve diverted the electricity from the power plant and are using it to lure the Rotom, and they even manage to catch one. But our heroes have a plan to combat this electric menace: they all have Ground-type Pokémon, which aren’t affected by electricity. With the help of Krookodile, Excadrill, and Stunfisk, they send Team Rocket blasting off again and free the trapped Rotom!
Professor Oak notices that Rotom is throwing sparks and seems to be injured, so he applies some medicine. This makes Rotom very happy, and when the professor asks if it would be willing to come with him and help with his research, it hops right into his Poké Ball! Mission accomplished!
Suddenly, the lights in the Pokémon Center go out. Although Ash, Iris, Cilan, and Professor Oak are surprised, the other people in the Pokémon Center are completely unsurprised. Nurse Joy explains that the Rotom on the island find the local power plant's electricity delicious, so the lights are always flickering on and off. In addition, the island's Rotom used to play pranks on the people of the island, so the locals created a playground of electrical devices where the Rotom could play without bothering anyone. Professor Oak goes with Ash and his friends to this electrical playground, where they see three Rotom traveling through the power lines. Pikachu drives them out with a Thunderbolt attack. Despite Professor Oak's request that they assist him with his research, the three Rotom proceed to cause as much mischief as possible. They taunt Pikachu, causing the latter to use Thunderbolt again, but they simply eat the electricity and enjoy it very much. Professor Oak then takes advantage of the Rotom's distraction to try and catch one of them, but the attempt fails. Much to everyone's surprise, Rotom shocks the professor, but Oak just laughs.
Rotom keeps sending electrical attacks at Professor Oak, but the professor apologizes for startling Rotom and invites it to shock him as much as it wants, something that surprises Rotom greatly. Per Professor Oak's request, Cilan calls on his Stunfisk to provide electricity that will lure in the Rotom, but the Rotom hate the taste of Stunfisk's electricity. Iris has her Emolga try next, and Emolga's Discharge is very tasty to the Rotom. Emolga tries to use Attract on the three Rotom, but it fails due to Rotom being a genderless species. The Rotom then enter a washing machine, a microwave, and a lawn mower. They all chase after and attack Iris and Emolga, and Iris recalls her Pokémon. Before the Rotom decide to leave, Ash quickly orders Pikachu to provide more tasty electricity for the Rotom to eat. However, only the Mow Rotom eats Pikachu's electricity, because the Wash and Heat Rotom both prefer Emolga's Discharge.
While Professor Oak and the others try to decide what to do next, all three Rotom turn around and begin eating obviously delicious electricity from an unknown source. They discover Team Rocket providing this electricity to entice the Rotom to come to them, and Team Rocket recite their motto. Team Rocket's devices are hooked up to the power lines, so they are feeding the Rotom fresh electricity straight from the generator, and Pikachu's electricity is insufficient to divert their attention. Team Rocket create a large ball of electricity with their sinister machines, attracting the Mow Rotom to try and eat it. However, the electrical energy is too great, and Rotom is forced out of the lawn mower and then dragged into a special box that effectively confines it. Using the electricity from the Rotom they captured, Team Rocket forces the other two out of their respective appliances. They immediately take possession of a refrigerator and electric fan, and Stunfisk, Excadrill, and Krookodile, being Ground-type Pokémon, intervene to prevent the Rotom from being pulled out of those machines as well. Seizing its chance, the Frost Rotom freezes Team Rocket with Blizzard, and Pikachu and the Fan Rotom use Iron Tail and Air Slash, respectively, to free the captured Rotom. The other two Rotom leave their appliances, and then all three of them send Team Rocket blasting off together.
The Rotom that was temporarily held by Team Rocket approaches Professor Oak, who treats its injury. Rotom confers with its friends and agrees to return with Professor Oak and help him with his research. The professor catches it in a Poké Ball before reciting a poem to commemorate the occasion. That evening, he offers to fly Ash, Iris, and Cilan back to Kanto with him, but they decline, opting to continue their journey by ship instead.
When Ash turns around to talk with Porter, the blue portion with a black strip on the back of his hoodie is missing.
When Wash Rotom uses Hydro Pump on Emolga, the white and yellow colors of Emolga's left ear are swapped.
In the scene where Rotom is being pulled into Team Rocket's trap, the Team Rocket logo is missing from the device.
Ash's hoodie error
Professor Oak's Pokémon Live Caster is localized as Professor Oak's Who's That Pokémon.
Since the narrator and Professor Oak don't share their voice actor in the English dub, Professor Oak interrupts the narrator and recites the "...as the journey continues" line himself; unlike the Japanese version which has the narrator impersonating Oak.