On Planet Flora, There are life stars in the holes. To get them, go up to the cliff, above the hole, and fall, excect fall a little closer to the wall, so close that your in the wall a little. Make sure there aren't any enemies around like Orblets and go for it!
On Planet Automation, Area 2, there are 1-ups and other stuff. In the section with the Mommy Orblets(I geuss that's what there called, They Throw those Eletric Orblets at you.), Headbutt them and fall in the hole and grab the little 1-up.
In the last section of the level, there is a little gap at the top. First Destroy the rhino, and then climb up there. When you get to the top, there are some Mommy Orblets. Destroy them, and fall in the hole. There is a Tri-Life Star, Super star, Yellow Diamond, and a 1-up. Grab all of them! But watch out for some Mommy Orblets.
In Planet Freon, Area 2, There is a 1-up when you enter the tower, but it's trapped at the top, so, go thru the level as you would do usually, except at the end, when you get on the star handle, go the other way, go back to the tower, and get on top. When you get on top, walk to the beginning until you find the hidden 1-up. You may have lost your Height Bonus But it's worth it! On Planet Sonata, When you give all the metromones to the birds, on the 4th one, when you here the drums, wait for a while, pretty soon you'll be hearing a very familiar theme, does the word Mary comes to mind?