My brother and I played the game so much we were able to beat that stage co-op. It gets much worse later. I learned not that long ago that the reason we were never able to beat it co-op is there's a bug that prevents the 11th stage from being beatable with two players.

You have to memorize the level and jump a bit before that one tricky one comes on screen.

Child me could beat it after hours of repeated attempts and running out of continues.

Adult me went back after a decade. The muscle memory was still there and I beat it on the first try. I probably got about an 80% success rate on first attempts now. But level 4 and beyond I'm terrible.

I only got it by state save scumming in zsnes, and even then it was tough not to save yourself into a corner.