Here's another one courtesy of David Wonn's Unique Glitches. Walk up to any of those boulders that Chunky can carry while charging your B-button move. Chunky will grab the boulder and toss it over his head. While the boulder is in the air and before he catches it, let go of the B button. If you timed it just right, Chunky will belch and the boulder will crash to the ground. But when Chunky's done belching, he'll be walking as though he's carrying the boulder!
It makes him look either like a zombie or he's sleepwalking.
In the Creepy Castle level, take Chunky into the Museum. He can see his reflection in both of these windows near the entrance.
Run into the back room and grab the boulder out of the skullhead's mouth. Carry it back to the windows, and...holy crap! The boulder has no reflection!
ARRRGGHHH! Evil Undead Boulder!!
Try standing on it and look at your reflection.
Your reflection is standing on nothing!
Incidentally, that object in the back of the room behind the window is the "strange pillar" that a lot of DK64 players had been wondering about. I don't really know why it's there, either, but I honestly don't think it has any purpose. It seemed to me to be there to help Tiny get closer to a purple banana balloon. (Although, I don't think she really needed the extra height of the pillar to reach it, but I think Rare just probably thought the room looked better with a pillar than with nothing at all. It is a museum, after all...)