I just remembered one thing about this game. I remember that ten years ago when I got this game I encountered a glitch or bug, whatever. It is the same trick that is used in the published run in level 2-1. The difference is that while playing bored I did it in level 1-1. I'm not sure if it is already discussed here or in the SDA, but anyway I'm going to explain it a little. I think this would shorten level 1-1 or perhaps someone finds out what causes the glitch and therefore it could be used in other levels too.
My own cart was bought in 1995 and it is PAL version. I know there are versions 1.0 and 1.1 around, and I think mine is 1.0. Not to mention: I have pulled off this trick more than once. If I recall right, I did it another time because it was so much fun.
I took a shot to reduce the amount of writing:
http://koti.mbnet.fi/jsp_/yoshi.png
The thing is that if I remember correctly, I stomp-jumped (press down in air) many times on the stones under the arrow sign. I'm only sure that the glitch happened when I landed on the area made by those two blocks. The enemies were propably killed, because I was doing this weird thing. What happened next was that Yoshi was taken to the sky (same, long room as in the movie), I always died there, because the room has really wide pit. I tried to hover to the far right, but I couldn't back then. I'm pretty sure it is the same room as in the currently published movie, and if Yoshi could hover to the far right, Yoshi would end near the end of level 1-1.
I tried to reproduce this glitch with Zsnes, but I failed (didn't try long though). I tried it also tool-assisted, but I don't have a clue how you people do it :)
I hope someone would try this, and I also hope this would prove to be useful.