Learn how to make big Bullet Bills appear just like in Mario World as well as those bomb platforms from Yoshi's Island that blow up after jumping on them a few times.
Learn how to properly do fireballs, make platform movement enemies and mushrooms, and make it so that a mushroom goes in a specific direction when hitting a ? block. Great how-to if you have MMF.
Learn how to make those rotating spike platforms from Yoshi's Island. If you hit one of the arrow blocks, the platforms of the respective color will flip over. UPDATED: Missing.