You go to Level Editor. Then, you can choose what background you want, your size, even hack the game by editing the code.
super mario brothers
When you are on the game, click on Level Editor and there you go!!!
I think you have to make a acount first
Go to the "Save"-menu and choose "Set flag pole".
Well there is this Super Mario World Level maker on the intenet called Super Mario Flash. You can make Super Mario World levels on your computer/laptop and share it with other people worldwide. Here is the link to it if your interested: http://www.pouetpu-games.com/index.php?section=2&game_id=1&w=640&h=480
Make your own flash and songs, stop stealing.
Mario level designer
Make an mc and type "onClipEvent (load)} Makeground(1) }"
yes
Blue mushrooms in New Super Mario Bros. make you small.
All you do is type Super Mario 63 (Level editor) (Of course you will loose everything in the one that you have and you will have the level editor though but loose all saved files.) There is another way (Go and make your level you can always come back and play on the previous Super Mario 63 that has no level editor but still have Saved Files
there are a few ways but it seems the most popular is by getting a copy of adobe flash and creating it from scratch or with existing sprites ripped from the games on a rom.