Harry
A small dragon, similar to the Hungarian Hornback Harry defeated in the tri-wizard tournament.
Ron
A snake, same as your brothers. Ron said it showed you were a true Slytherin, not just put there because of your blood status.
Hermione
An Otter, the same as her own.
Draco
A white ferret. When Mad-eye transfigured Draco in your fourth year, you couldn't stop laughing.
Luna
A white rabbit, similar to her hare.
Fred
A Badger, like your house animal.
George
A doe, like your mothers.