What game was Super Mario Bros. 2 built from?

What game was Super Mario Bros. 2 built from?
Screencapture // Wikimedia Commons

Perhaps even more so than in the movie industry, when a video game does well, you can rest assured that a sequel will follow.

And there have been some great sequels in video game history — I mean, the first Grand Theft Auto was fine, but the sequels…

Naturally, when Super Mario Bros. for the NES became insanely popular across the world, a sequel was sure to follow. And it did! But, Nintendo execs thought the advanced gameplay of Super Mario Bros. 2 would be too difficult for American gamers. So, they did the next best thing — rip off a different game, lightly skin it with Mario stuff, and call it a day (in fairness, they couldn’t really rip it off since they owned it, but whatever, it was lazy).

So all those years, you were actually playing this other game — any idea what it’s called?