A team of modders has released a fan-made prequel to the original Metroid.
After Metroid's 30's anniversary passed without much attention from Nintendo, the team decided to deliver its own take on the events that unfolded before Samus’s famous Zero mission on planet Zebes. The original Metroid manual tells about a deep-space research spaceship that was attacked. Pirates seized a capsule said to contain a newly discovered life form in a state of suspended animation. Rogue Dawn surrounds these events that led up to the theft of the capsule which ultimately placed the Metroids under the control of Ridley and the Mother Brain.
Nintendo's legal team typically takes down similar games within hours of release, but the team is trying to protect against that by releasing the game as a modification for the original Metroid NES ROM rather than releasing it as a standalone executable. Unfortunately, there is really no guarantee that Nintendo will not take it down anyway.
If you are a Metroid fan, make sure to download Metroid - Rogue Dawn and follow the instructions to run it.