Back in the '90s and 2000s, it was quite common to see Chinese or Taiwanese-made bootleg games for consoles such as the NES, SNES and Game Boy.
One such example was Zook Hero, a franchise made by Taiwan-based developer Vast Fame which basically ripped off Capcom's Mega Man franchise. While these games were unlicensed in nature, they were often of a very high quality; the Zook Hero series has a lot of fans.
However, the third entry, Zook Hero Legend 3 (AKA Zook Hero 3, Rock Hero Legend 3 or Super Rockman, depending on which version you're talking about), was almost a clone of a clone; developed by a company called Sintax, it was based on Vast Fame's games but wasn't as good.
Here's some background, taken from the excellent Handheld Underground:
This game was released in 2004, when Sintax was past their prime, but hadn't quite descended into the lows they'd reach in the subsequent years. Accordingly, it does make a serviceable effort to mimic Mega Man (but not Mega Man X) gameplay, and makes the fairly neat addition of a Metroid-style morph ball move. But it inevitably doesn't come anywhere close to reaching the high standards of Vast Fame's original Zook games. The music is taken directly from the official Game Boy Mega Man 2, so it at least comes from an appropriate source, but that is considered one of the poorer soundtracks in the series and again it doesn't really match up to Yishen Liao's work on the original Zook games.
Despite this, the game has become a rare collector's item and has remained undumped – until now. If you fancy checking out this insanely rare piece of bootleg history, head over here.