It’s common knowledge among Pokemon fans that a climactic showdown with Professor Oak was originally planned for the series’ inaugural duo of games, Red & Blue. The reasons as to why this was eventually cut are unknown to this day, although we can tell it was most likely intended to be one final battle after becoming the Pokemon League champion. There’s quite a bit of evidence supporting this from both Red & Blue and other Pokemon games, but the circumstances of its absence are largely unimportant when compared to what actually matters here - that Oak’s fight being hidden is emphatically what makes it so great.
There are a couple of different ways to instigate the Oak fight in Red & Blue, but the easiest method involves combining the infamous old man glitch with the equally infamous Ditto glitch. While said glitches might sound complicated, they're actually fairly easy to replicate. The best one is obviously still Mew’s truck, though.
Anyway! In short, the glitches you need to trigger the Oak battle revolve around including certain characters in your name, manipulating the game’s reaction times by using the long trainer glitch, and exploiting the coast of Cinnabar Island given that the tiles separating the land from the water are for some reason listed as grass tiles. I could get into the nitty gritty of how it works here, but all I’d be doing would be posting a dense blow-by-blow that isn’t really conducive to my main argument. If you want to battle Professor Oak in Red & Blue for yourself, the video below offers a pretty solid, short, and easy-to-follow guide.
Once you’ve set up the fight by following all of the steps above, you’ll be able to take on Oak once and for all. Narratively, this is a remarkable endgame event that absolutely should have made it into the final versions of Red & Blue that shipped. After getting your first ever Pokemon from the local professor, it’s only natural to round out the story by defeating him - especially when you consider his past as a trainer, and the email at his PC suggesting that he himself was the Pokemon League champion before redirecting his energy towards research. That’s not to mention the fact he’s always trying to chat up your mam - get out me gaff, bud. Let’s take this outside.
Oak’s team is also intriguing. While his fully evolved starter depends on the number of stages you lower Ditto’s attack by during the setup - if that’s confusing, it’s explained in the video I linked earlier - his other four ‘mons are Tauros, Exeggutor, Arcanine, and Gyarados, three of which Blue, your rival, also owns. The difference is that Oak’s ‘mons are all quite a few levels higher than Blue’s, further hinting at the idea you were supposed to fight him after having already become the champion. Interestingly, Pokemon Masters EX has since revealed that Oak’s favourite Pokemon is his Nidorino - which makes sense given that the original Gen 1 intro is supposed to be Oak’s Nidorino against Agatha’s Gengar - so it’s a bit weird to see either it or a Nidoking missing from his squad, but then again it’s also weird that the whole battle was cut, so what do I know? What is worth noting is that the inclusion of Tauros feels like a deliberate nod to the fact Ash catches 30 of them in the anime and decides that, actually, he wants none of them, so he sends them all to Oak and they just knock about a little field for all eternity. It’s nice to see the professor taking a shine to at least one of them, eh?
Still, this particular omission is a fascinating one. Obviously things get cut during game development all the time - from over ten unused alien species in Mass Effect Andromeda to a bunch of additional origin stories from Dragon Age, it’s not uncommon for dozens of ideas to get scrapped during the creative process. What makes this Oak battle so weird is that it’s still literally in the game. His Pokemon are there, the battle functions if you manage to trick the game into displaying it, and the leveling gives us a fairly decent idea of whereabouts in the story it should have occurred.
My gut says that it’s not actually immediately after beating the Pokemon League, but instead has something to do with Mewtwo - maybe Oak was originally supposed to be the guy who tests you before you gain access to Cerulean Cave, or perhaps after capturing Mewtwo he wanted to battle you in order to ensure you’re sufficiently capable to train it properly. Either of these options would have made the already excellent Cerulean Cave section even better, although this is admittedly just retroactive wishful thinking - educated wishful thinking, mind, but wishful thinking nonetheless. As it stands, the only way to trigger the Oak battle is to use a variety of glitches that manipulate the game into reading it. While that’s sad, it’s also indirectly contributed to some kind of cryptic mythos surrounding the fight - like MissingNo and the Pokemon who are over level 100, it’s the intrigue and mystery that makes this specific battle so enduringly special.
Would I have liked for Oak to have been given the narrative significance he deserves? Absolutely. Going back in time now, though, would I knock on Game Freak’s door and attempt to convince the devs to put Oak’s battle back in? Nah, probably not.
The hidden battle with Professor Oak’s is still one of the most brilliant strokes of genius Pokemon has ever managed to pull off. Most of that brilliance is accidental given its nature as a sequence that cannot be accessed without the use of various glitches, but hey, an accidental victory is still a victory.
Wait - what are you still doing here? Go find your copies of Red & Blue and crack out the AA batteries for that dusty old Game Boy in your cupboard. 25 years on, it’s a better time than ever to beat up Gary Oak’s grandad - even if you’re technically not supposed to.
The student who acquired the drive has been given a life sentence and others who watched it will do five years hard labor.