First, there's the one in Howzit's store in World 1-2, you know, the Shadow World one? Goooooooood times, goooooood times (lol get it cuz howzit says gooooooood all the time amirite). I wish the "Shadow World" was larger, though. Also, when doing this glitch, I was able to talk to Howzit from outside his door.
Second, I found this glitch on Youtube where you can swim in the air in the Underwhere (7-1) by doing some flipping by the fountain. I'm not good at explaining, so you'd be better off looking it up on Youtube yourself. It's worth the look; watching Mario and Co. swim through air is priceless.
Got any other weird glitches for me to check out~? Share your tales of Super Paper 'Glitchiness' here!
Go to the store in... I think it was 1-2 or 1-3... and flip. Walk to the corner by the door (If you just walked in go up) and un-flip. Mario will do his "Press 2 to not die" dance and he'll fall and get hurt. Also, I dont know how to do it, but you can walk into the blackness if you do it right.
The only one I did was the Return Pipe glitch. Where you walk and pause while Mario's walking and hit the Return Pipe. Mario continues to walk as he spins. That was a mistake, though.
I once got a variation of the first one that came up completely randomly, and not everything was black. Also, going into houses somehow got them changed to Howzit's store at some parts. I might still have the video...