Use Demoness and go into any level. Perform the manual "Visiting Home" when she is special. When she is below the ground, skate up a ramp and press Y when you reach the lip to do a lip trick. It may take a couple of tries, since she tends to go into grinds when she's underground. But, after doing it correctly, Demoness will go above the ground, but she'll be invisible. You can still see the board, "religious table" and fire. You can skate around like this performing tricks, and you can even smash into people. But, if you perform a grind or manual, she'll turn back to normal. Also, she'll just sometimes randomly turn normal after doing a jump.
Submitted by: jigglypuffer