Meh, not bad
What it could use: Music and better singing.
Yes, it needs some sort of beat to it. And the way it goes "Malfoy! Malfoy!" could use some work... Try listening to the original work to get it perfect. Also, the ending (It's a snake!) comes after a few loops (ie. Potters, Malfoy, Potters, Malfoy, Potters, Malfoy, Potters, SNAPE!).
Other than that, come up with something cool and original.