Coins appearing exceedingly high in the air after defeating monsters.
http://i4.photobucket.com/albums/y127/11246/coinsbugSK.png
This was on the second Jelly Castle level. It's easily reproducible by
1:Destroying the bush on the grass
2:Then killing a monster in that area.
The coins still attract to the character normally, so this is low priority.
That actually occurs in a lot of other places as well. When it happens to me, I notice that there is usually a monster or destructible object in the space where the crowns would have fallen, and the monster/object moves away/is destroyed, leaving the crowns up in the air like that.