One of Pokemon Legends: Z-A's most important items may have first surfaced 12 years ago as unreleased content in X and Y, suggesting a certain Mega Evolution may have been in the works for over a decade

It sounds like one of Pokemon Legends: Z-A's big plot points could have been over 12 years in the making, with an unreleased item first found in Pokemon X and Y bearing a striking resemblance to something that's just now been included in the real-time RPG.

Be warned, there are spoilers ahead for one of the endgame moments in Pokemon Legends: Z-A, including a story-centric new Mega Evolution – proceed with caution if you've not already rolled credits.

During the events of Pokemon Legends: Z-A, the legendary Pokemon Zygarde takes an interest in the protagonist, and ends up giving them a key item simply called "Pebble." Described as an "ordinary pebble" that's "completely unremarkable," at first it just appears that the 10% Forme of the 'mon is behaving as dog-like as it looks by bestowing a 'treasure' upon you, but it later transforms into Zygarde's Mega Stone, the Zygardite, leading to an incredibly cool scene involving Mega Zygarde.

While Mega Zygarde is a new addition to Pokemon Legends: Z-A, there's some speculation that this whole idea could have been in the works for a long time. Highlighted by the Bulbapedia Twitter account, there's an unreleased key item, first discovered in the previous Kalos region games X and Y, called the Common Stone. It was never officially released, but its item description sounds rather familiar: "A perfectly normal stone that might appear valuable to some. It's all in the eye of the beholder."

Perfectly normal, huh? Not only does it look an awful lot like Z-A's "Pebble," it's worth noting that this item description is also similar to that of the Intriguing Stone key item, which turns out to be a Mega Stone for Pidgeot in Omega Ruby and Alpha Sapphire. Coincidence?

The thing is, this wouldn't be the first time Game Freak had included something in a Pokemon game that ended up being a hint of something to come in the future. The Strange Souvenir item is perhaps the most famous – added in Generation 6 and initially described as "an ornament depicting a Pokémon that is venerated as a protector in some region far from Kalos," it was later revealed to be a hint for the following generation's Alola region.

Whether that's the case here with the Pebble is another matter. After all, the item was never actually available officially. But hey, it's an interesting matter to speculate – perhaps Mega Zygarde was originally meant to be added a lot sooner than it actually was, but it took the return to Kalos in Legends: Z-A to actually make it happen.

You can read our Pokemon Legends: Z-A review if you're yet to pick up the new real-time RPG, or check out our Pokemon Legends: Z-A tips for some pointers to get you started.