Pro tip: An invisible secret nothing in Super Mario World

You remember the Top Secret Area in Super Mario World, right? Well, it's got one more secret up its sleeve.

Take a look at this screenshot.

Looks pretty normal, right? But I'd like to draw your attention to this area about in the middle of the screen, toward the bottom.

If you take Yoshi and hold Up while pressing Y, his tongue will shoot out, but he'll be standing up.

If you're positioned correctly, you'll hear a 'thup-thup' sound, like his tongue is bouncing off of something that he can't eat, like a keyhole. But there's nothing there.

Weird, huh?