To Catch a Rotom! (Japanese: ロトムVSオーキド博士！ Rotom VS Professor Oak!) is the 31st episode of Pokémon: BW Adventures in Unova and Beyond.
Arriving at another island, Ash and friends meet Professor Oak there. Professor Oak is on the island to do research about the Rotom changing their Forme. The group finds three Rotom. These Rotom change Forme, but they turn out to be the real troublemakers. Even with Team Rocket getting involved as they attempt to steal the Rotom, will Ash, Professor Oak and the others calm the Rotom down?
The heroes see the Torom island. Porter warns them to pack things now if they want to board off the ship in time. Cilan and Iris cannot wait to meet the expert on the world of Pokémon and the most known researcher. The heroes wave hands, as Prof. Oak came to meet them. Ash greets Prof. Oak, who is glad to see him and Pikachu. Cilan introduces himself to Prof. Oak, who is willing to hear his evaluations as a Connoisseur. Iris also meets Prof. Oak, who thinks of her as a high-spirited girl. Team Rocket, in their submarine, is surprised to see Prof. Oak, so Meowth suspects he came from Kanto to see a rare Pokémon. At the Pokémon Center, Oak announces he came here to catch a Rotom, which are common to see here. Ash shows Rotom on his Pokédex for Iris and Cilan, since he met one in Sinnoh region.
Ash asks Prof. Oak why does he want to catch a Rotom. Oak replies it is for his article he needs to write about Rotom's form changing. Iris and Cilan wonder about these form changes, so Oak gives them a presentation. Rotom's mischievous nature causes it to infiltrate electric devices. When entering an oven, fridge, lawnmower, fan or washing machine, Rotom takes the form and changes its appearance. Iris is surprised Rotom has so many forms, while Oak continues on. A toy robot started to move, making the scientists to believe it was a new type of a Pokémon. However, the robot disappeared, so it was assumed this was Rotom's work. Team Rocket overhears this and Jessie has a plan: to catch their own Rotom. She thinks it could power their machines they construct, pleasing James and Meowth.
The heroes decide to help Oak find and catch a Rotom. Suddenly, lights stop working, so the visitors of the Pokémon Center think "it is time for lunch". Oak is certain Rotom is "having lunch" - Nurse Joy explains Rotom "eat" electricity, thinking it is delicious. When over, Rotom enter other people's devices and scare people away. Since the people were terrified, they built a playground for Rotom, full with devices they can merge with. Team Rocket spies on them, planning on catching their own Rotom. Pikachu senses something, as the wire starts flickering. They notice two more, tempting Team Rocket to catch all three Rotom. Pikachu uses Thunderbolt on the wires, causing Rotom to respond and appear out of the wires. However, the Rotom start laughing, for one pokes Pikachu, causing him to use Thunderbolt. Surprisingly, they eat Pikachu's electricity.
James believes the Rotom could help them catch Pikachu, while Meowth thinks the best way to catch them is to lure them with food. Oak throws his Poké Ball to catch Rotom, who struggles and comes out. Rotom hits him with Thunderbolt, but Oak endures this. Iris is surprised to see Oak this resilient. Oak replies he deals day by day with all kinds of Pokémon back in his lab and could resist this tiny spark. Oak, despite struck with Thunderbolt, lets Rotom know he wants to be his friend. Oak asks others to send their electric-type Pokémon to lure Rotom closer. Cilan sends Stunfisk, who uses Thunderbolt. Rotom eat the electricity, but don't find it tasty from Stunfisk. while Iris sends Emolga. Rotom electrocutes Oak, who apologizes, since he did not think Rotom would like Stunfisk's electricity. Iris sends Emolga, who uses Discharge. The Rotom like Emolga's electricity and chase her to get more. Emolga retaliates with Attract, but there is no effect, since they genderless; nor male nor female.
Suddenly, Rotom start entering the electric devices, becoming an Wash, Mow and Heat Rotom. Emolga runs off, causing the Mow Rotom to go over Stunfisk and use Leaf Storm on Emolga. Emolga lands into Iris' hands and both are hit by Overheat and Hydro Pump. Oak sees when entering the devices, the Rotom gains a new move. Iris calls Emolga back, while Oak asks Ash to power the Rotom with Pikachu's Thunderbolt, else they may leave. Cilan notices the Mow Rotom ate Pikachu's electricity, but Wash and Heat Rotom did not. Suddenly, they turn around and eat more electricity, for Team Rocket appears to supply them with electrical energy from the power plant. Team Rocket repeats their attacks, since they want Rotom to be on their team. Pikachu uses Thunderbolt to gain Rotom's attention, but Team Rocket releases electricity to counter the move.
Team Rocket continues supplying Rotom with electricity. They merge their beams, causing the Mow Rotom to be attracted to it. However, the power is too strong, causing Rotom's lawnmower to be detached from it and to be captured into Team Rocket's cage, on which Jessie places a seal. Team Rocket is proud they got one, but won't leave without the other two. Draining Rotom's energy, Team Rocket hits the Wash and Heat Rotom, causing the appliances to be detached. The two Rotom enter the fridge and fan, becoming Frost and Fan Rotom. Ash, Iris and Cilan send Stunfisk, Excadrill and Krookodile to take Team Rocket's electrical attacks. Frost Rotom uses Blizzard, freezing Team Rocket. Pikachu uses Iron Tail and Fan Rotom uses Air Slash, destroying the machine and freeing the third Rotom. Rotom use Thunderbolt, blasting Team Rocket off.
Seeing Rotom injured, Prof. Oak sprays the potion on it. Rotom is glad, so Oak proposes it could go with him to study it. Rotom goes back to two of its friends, who agree it could go with Prof. Oak. Oak touches Rotom with the Poké Ball and catches it. The heroes are glad, while Oak tells the other two Rotom to visit them someday. Later, Oak tells the heroes they can travel by his plane, which will take them to Kanto right away. The heroes decline, since they can encounter new Pokémon by traveling around the islands. While the two Rotom play and fly off, the heroes bid farewell to Prof. Oak, who flies off.
- Professor Oak's Pokémon Live Caster: Rotom (mid-episode) and Gigalith (end of the episode)
- This is the first time that two different Live Casters are in the same episode.
- This episode marks the first time that someone mentions the existence of genderless Pokémon in the anime.
- Though not exactly a boss fantasy, this is the first time in the Best Wishes series that Team Rocket fantasizes about the Pokémon they are planning to steal.
- The beam emitters that Team Rocket use to capture Rotom are similar in design to the Proton Packs from Ghostbusters.