The star block: if there are red coins on the level, a red spark will circle the block for each coin you haven't gotten. When you get all of the coins, you can hit the block to access a secret level.
As for the suits: the Luigi suit comes from a Luigi cap. It can jump higher than normal and do the crouching high jump from Mario 2. There're two in the game.
The goomba suit is gotten from brown mushrooms. It lets you walk on those painful plants and also turn into a goomba (down and button 2,) short, slow, and invincible to enemies. There are two of these as well.
I also made a monkey suit (it's a tuxedo. Bad pun.) and a hammer bros. suit. However, there are no monkey suit items in the game, and the hammer bros. suit is very hard to find. If you do find it, I'll give you a golden cookie.
There were other items too, but there's no way to get them in the game.
Absorbed in the clouds, a voice from afar said
"With the right device you can make a pattern grow,
or you can tune up your car."