So today while duelling I have discovered that while there is a activated frost trap on the ground and your ghost wolf is standing on that area he becomes invisible, it can be seen only from certain camera angles. I didnt check yet does it work for other people too, but if it does its a nice way to confuse your opponents with invisible pet
Screenies:
http://img526.imageshack.us/img526/2...7174739ll7.jpg
http://img102.imageshack.us/img102/6...7174744ne9.jpg