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Given the widespread fame of the Zelda series, you would assume all of the series' secrets would be common knowledge these days, but with the passage of time, it's becoming clear that some of its hidden features aren't as well known as others.
For example, Twitter user TheRealPit0 appears to have surprised a few people with the revelation that there's a secret shop in Zelda: Oracle Of Seasons / Ages on the Game Boy Color that can only be unlocked by inserting the game into the Game Boy Advance.
According to the Zelda Wiki, the store is found next to the Lynna Village Shooting Gallery in Oracle of Ages, and the Know-It-All Birds' Hut in Oracle of Seasons. Every item in the shop costs 100 Rupees, and it stocks a Gasha Seed and two Magic Rings.
This store isn't accessible in the 3DS Virtual Console version of the game or the Nintendo Switch Online version, which makes it quite a unique unlock – and this has no doubt contributed to it becoming a forgotten secret in the history of the series, at least with newcomers.
Thankfully, it can be unlocked in emulators, and there's even a special modded version which unlocks it.