Super Mario Odyssey's Metro Kingdom and its New Donk City were seemingly bizarre additions to the series considering the other, much less "realistic" worlds Mario has travelled to over the past 30 years. Populated by citizens who look more like real-life humans than Nintendo's cartoonish Italian plumber and his pals, seeing Mario walking side-by-side with suit-wearing businessmen and women, bouncing on yellow cabs and clambering up skyscrapers was certainly a different approach for Nintendo to take. However, after playing Super Mario Odyssey it's clear that Metro Kingdom may not be such an off-the-wall design after all.
As with most real-world cities, New Donk City appears to be in a perennial state of reconstruction. Consisting mainly of towering skyscrapers a la New York City, there are still many steel beams located throughout Metro Kingdom, which Mario mostly uses to hop to new platforms in order to get his hands on those all-important Power Moons. However, those steel beams are also of great relevance to Mario's history, with the secret behind the Metro Kingdom seemingly changing up a few things in the franchise's lore.
During your time in Metro Kingdom you'll meet Mayor Pauline, best known for her appearance in the Donkey Kong arcade game in which she was kidnapped by the giant ape. Curiously, Pauline doesn't appear to recognize Mario, though if you talk to her near the city hall she will send you on a mission to retrieve her backing band. After doing so, you can venture beneath New Donk City in order to turn on the power supply for a festival, which is intended to "celebrate the history" of New Donk City.
This festival is essentially a recreation of the old-school Donkey Kong game, with Mario walking along construction beams and hopping over barrels before eventually thwarting the ape. The implication is clear; New Donk City was the setting for the original Donkey Kong arcade game, with the ape capturing Pauline while it was still under construction all those years ago, before she somehow became mayor following this event in a city apparently named after the beast that kidnapped her.
However, there's still one mystery that remains unsolved: why does Pauline not know who Mario is? In the Donkey Kong arcade game, Mario was initially referred to as "Jumpman" while Pauline, then named "Lady," was his girlfriend. Considering that Jumpman rescued Pauline from the clutches of the ape, an event that she describes as "traumatic" in Super Mario Odyssey, you'd think she'd remember him when he visits her city. But what if Mario isn't Jumpman?
Up until this point Jumpman was the original moniker for Mario, with the name of the character being changed for the home console version of Donkey Kong. But Super Mario Odyssey appears to suggest that either Pauline is highly forgetful, or that Jumpman and Mario are actually two different people. Another theory is that perhaps this Pauline isn't the Pauline we saw in Donkey Kong, but that's disproved in a later conversation with the mayor when she asks you to recall something she did "a long time ago," with the answer being "captured by ape."
Pauline has appeared in Mario games before, with her having been captured by Donkey Kong again in the Mario Vs. Donkey Kong series. However, much like the Mario series' various spin-off sports titles, Mario Vs. Donkey Kong isn't regarded as fitting in with the Mario series' (admittedly very loose) canon. If that's the case, then Mario and Pauline have never encountered one another in the core Super Mario series, and their only relationship was when Mario was known as Jumpman. If Mario isn't Jumpman, then the pair have technically never met in a main Mario game before, making her failing to remember him much more understandable as they have technically never met.
Of course, the Mario canon isn't as heavily deliberated over as the likes of The Legend of Zelda series, and Shigeru Miyamoto himself has stated that it's best to think of every Mario character as actors in a play. In an interview with Game Informer back in 2012, Miyamoto said: "If you're familiar with things like Popeye and some of the old comic characters, you would oftentimes see this cast of characters that takes on different roles depending on the comic or cartoon. They might be businessman in one [cartoon] or a pirate in another. Depending on the story that was being told, they would change roles. So, to a certain degree, I look at our characters in a similar way and feel that they can take on different roles in different games."
But while Nintendo doesn't stick to a strict canon and chronology with the Mario series, there has always been some semblance of an overarching story between the games. As such, Pauline's failure to recognize Mario is either indicative of Donkey Kong not being classed as part of the Mario canon — which wouldn't make a great deal of sense, considering Pauline still remembering the events of the game — or of Jumpman and Mario now being considered two separate people. Either way, New Donk City is now an established and important part of Mario history, along with its oddly incongruous race of humans.