Hey, I was just playing this game (normally) and I found this awesome glitch. In level 2-1, just after the middle-ring, there is a giant tramboline ball that you take to the top, and there are some blocks in the air also, forming a line (so you can't jump outside the lines). Meh, it's hard to describe, so look at this picture (far right):
http://www.vgmaps.com/Atlas/SuperNES/SuperMarioWorld2-Yoshi'sIsland-World2-Area1(1).png
You can actually jump to the left of those blocks. It's very difficult, but in a timeattack that's obviously not an issue :) Just be running left when you touch the ball, then wait a little longer than normal, then jump. If you do it exactly right (and it WILL take LOTS of tries) you'll bounce up on the left side of the blocks. When you make it, you'll be transported to a completely blank area (just the background). Now "flap" to the right at least eight times and then just fall normally (pressing right at all times). When you fall to the bottom, if you did it correctly, you'll land in level 1-1 !!!
This could potentially save a little time since if you complete the level from there, it'll be as if you completed 2-1 and you'll advance to the next level. You can skip the autoscroll bit in 2-1 completely.
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