In the age of the internet, good secrets are hard to keep in video games. Code is datamined and thousands to millions of fans will try to catalog every little bit of information out of a title they can. Sometimes, however, something special slips through the cracks.

Over four years after the original release of Donkey Kong Country Tropical Freeze, a Twitter user by the name of Shane Marchis seems to have found something interesting. As far as I can tell, Marchis is the first player to find and publish this easter egg.

There, floating just above Donkey and Dixie, is an honest-to-goodness Metroid. While certainly not at home in a Donkey Kong game, the game’s developer, Retro Studios, is also the creator of the Metroid Prime trilogy and sneaking in an homage to their past projects is not completely wild. In fact, there is another (much more obvious) callback to the Metroid series in the game as well.

Hidden among the foliage in the background of one of Tropical Freeze’s levels is Samus’ ship. This one was, of course, less well-hidden than the swimming Metroid Marchis found.

So, how did he find it? A few hours after his initial discovery, Marchis posted another tweet, this time with a video detailing how the Metroid can be found.

In the level Amiss Abyss, Donkey Kong should progress until reaching a long, escalating, underwater tunnel. Once he has swam through it, he must swim backward through it again. You’ll find that the channel he originally swam through now has a stinging sea anemone guarding the passage back. Donkey Kong must push through it (he will take damage) to arrive back where he came from. If this is performed properly, the Metroid will appear.

We’ve confirmed that this works on both the original Wii U version of the game and the newly released Switch version as well. It seems so simple, but the game has been out for four years and no one seems to have picked up on it at all.

Who knows what other secrets lurk in games we’ve already relegated to the shelf?