Have you ever played Mario Forever fro PC, by Buziol Games? I have. There's one glitch I know of: at the start, you go into a place with 3 save pipes, which save at the start of each new world. You'll always start as Small Mario; however this is not the glitch. If you leave the screen to the right, you come to a non-hidden area with 2 powerups that you keep when you load: a Power Flower (cost 2 lives in next play) and a Mushroom (cost 1 life in next play). They are separated by walls, one between them and one on either side. Once you grab a power-up, you cannot grab the other. This is not the glitch. Grab the Power Flower, then from the wall on the far right jump at speed to the right and you'll land on a staircase going down. This is the glitch. Follow the staircase and keep going until you see a pipe. Jump over any obstacles then go down the pipe and you enter a special world with scientists replacing the creatures; scientists coming out of pipes, scientists running around to replace goombas, scientists throwing hammers...
Input on this?