Ingo, (Or Nobori in Japanese) a character that appears in Pokémon Legends Arceus, has surprised many fans with his recasting from an older game: Particularly Pokemon Diamond and Peral. The character’s background is never clearly explained in Arceus, but fans of older games will immediately recognize him and also his brother Emmet (Kudari in JP).
Ingo has stood in the way of B&W players before as the Subway Master. a facility where pokemon battles took place while riding a train. If players accumulated enough points or won on the train, they could challenge him, but also they could challenge him and his brother in a tag duel. While the character does not really have any impact on the story, he was still pretty popular among fans and included in a variety of merchandise items.

They have their own lore and dialogue if you want to full picture. They go on about how they shared a powerful dragon as heroes, and that one brother sought truth while the other sought ideals, and they eventually fought on how to use the dragon until it split itself into two, creating Reshiram and Zekrom, or in other words, the “Black and White” sides of the original game, so as not to separate them apart from each other.
Originally, that’s what had fans devastated when playing Arceus, because Ingo appeared again in the game Arceus but on his brother beside him. The theory though is that Ingo is not actually Ingo, but his brother Emmet. One of the reasons cited for the emergence of this theory on Japanese SNS was that some of the gestures performed by Ingo reminded them of Emmet instead.
One example is that the character here is touching the brim of his hat with his right hand, but in past works, it was his left hand, so it is said that emmet originally used his right hand. In the same manner, the character actually quotes some lines from his brother, though that might have differed in the English translation, so Japanese fans think Ingo has lost his memory and thinks he is his brother, and that they have cried because this identity crisis has made them more devastated than the original lonely hypothesis.

It’s unknown whether these theories have some truth to them, but it’s clear that game freak already knows of the popularity of these Duo, and that’s why they decided to bring them back. Maybe they will build upon that in the future, but all in all, interpretations like this are one of the important elements of enjoying any work in general, so Fans have been happy about all the possibilities they could imagine from this new counter with an old friend.