As the title suggests, I found a glitch that made my fly really far into the sky.
I was playing one of those "Troll Enemy-Spam Levels". I finally beat it, and I wanted to get a screen shot of me beating it.
I was excited when I finished, but when I exited photo mode, something strange happened. I couldn't move, and my character was stuck in the pose you see in the picture. I figured he was stuck in his animation, so I tried to trigger another animation by kicking (because nothing else would work). This launched me into the air, and I flew out of the arena. The only way I would stop flying away was to exit the level, which made me loose all of my hard-earned progress on this nearly impossible level.