Here are some pictures of a hack I made a while ago:
A secret Yoshi.
A bonus game Yoshi.
Luigi and Green Yoshi.
Luigi and Yellow Yoshi.
I changed Yellow Yoshi's palette so he doesn't look kind of orange.
Another map screen pic.
I fixed the map palettes and I deleted the map scrolling on the sides.
The glitch picture that you'll see every secret ending.
The left is Black and the right is White Yoshi. I need to fix it.
I haven't change any text except the Super Mario level. Crappy link
Edit: Here's an update.