i found this out with a friend, thought i could share...
this is a fun exploit wich does nothing much except getting a tiny mount
here is how you do it:
Find a friend who has the hallowed wand - bat
MUST be bat
meet eachother, you will mount (3 sec cast) and when you are mounting he will cast, when you are mounted he will cast the costume and you will turn into a bat, with a miniature mount underneath you! works with ANY mount :P
Hint: try a 2 or 3 man mount and get people in it, it looks ridiculous
(will try to upload a screen soon)