Ash’s adventures in the Pokemon anime may be coming to an end, but one fan is still baffled over a certain time paradox involving Ash, Pikachu, and Professor Oak. This particular conundrum first appeared in a 20-year-old movie, but its lasting implications still puzzle Pokemon fans to this day.

Pokemon fan and content creator Duwiol recently shared his befuddlement on TikTok. During the video, he explained the time paradox: in the 2001 film, Pokemon 4Ever - Celebi: Voice of the Forest, some time-traveling shenanigans cause Ash and Pikachu to meet a young Pokemon trainer named Sam. Together, the three save Celebi, the legendary time-traveling Pokemon.

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However, near the end of Celebi: Voice of the Forest, it is revealed Sam is none other than Samuel Oak–the very same Pokemon Professor who gave Pikachu to Ash in the first place. Professor Oak is also aware of the fact that these two Ashes are the same person, and thus made the active decision to catch Pikachu, invite Ash along with three other children to get starter Pokemon, and ensure the two were united. Duwiol was left to puzzle over the time loop that ensued from Oak giving Pikachu to Ash at his Pokemon lab because of Celebi: Voice of the Forest, while simultaneously only seeing the two during the film’s events because he united them in the first place.

This time paradox is a classic example of a casual loop, also called a bootstrap paradox. This theoretical proposition is one of the most common story beats in time travel narratives, and usually involves a person doing something that affects themselves in the past to eventually set them on course to repeat the same action in the future, creating a self-fulfilling prophecy with no true beginning. Though used in science fiction like Star Trek and Doctor Who, Zelda fans might also remember a similar bootstrap paradox appearing in Ocarina of Time surrounding the Song of Storms.

Duwiol’s fellow Pokemon fans enjoyed watching his confusion over the time loop. Some players wondered how much stress Professor Oak must have been under to catch the right Pikachu, while others joked this made Pikachu the original paradox Pokemon.

The Pokemon anime is coming to an end soon. It recently announced its 25th season would be the last chapter of Ash’s journey, after which it would follow the adventures of Riko, a brand-new Pokemon protagonist. Fans will have to wait and see if the new heroine stumbles into any time-bending hijinks of her own once the new Pokemon show begins.

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