So this is just a random question that came to me - besides the zones that I can think of off of the top of my head (being Green Hill Zone and Angel Island) are there any other zones (besides Green Hill in Generations) that have had stuff hidden in the trees? Edit: I'm talking strictly Item Boxes, no Badniks
I remember playing Sonic Heroes and coming across something like this in Hang Castle. There was a hint specifically stating that stuff was hidden in the trees and would be dropped by Fire Dunk/Fire Launcher. Despite checking nearly every tree, I could not find anything. Can't think of any others off the top of my head, though.
Sky High act 1 from 8-bit Sonic 2 has hidden birds that pop out from pine trees if you run against a nearby item box...which is pretty cool because it doesn't seem to serve any purpose at all. Oh, wait...cool as in 'cool powerup'? Nevermind then.
Well to broaden the subject. There is usually items hidden in all of the levels... Hidden behind scenery such as the floating monitor in the floor you drop through in the first section of Flying Battery. On top of loops in GHZ. In walls. Isn't that part of the game?
What a random question :v: I think we've probably covered it now. There's some hidden boxes in the walls of Marble Zone, and Sonic Heroes' Seaside Hill puts items in trees too, as well as springs and such. Not too sure if the Advance games do or not, I can't quite remember at the moment. They've usually got stuff hidden in passageways and things. Hell, Sonic 4 had one or two secrets like this too actually, but none in any trees.