Why does Harry Potter appear to be a glowing deer????

Rating: 7/10 (19 December 2004)

When Harry and Sirius Black are being attacked by the Dementors.....why does it look like a glowing deer that saves them....I Just don't get it.....also, when Peter Pettigrew is transformed from being a rat he is fully clothed...However, when he turns back into a rat, the clothes remain. I know these are trivial issues...but that glowing deer thing!!! What is going on there?
the Film is very good though, I think Michael Gambon should have studied Richard Harris' Dumbledore a bit more.....Talked a bit slower and had a calm demeanor....Don't get me wrong, He is a wonderful actor...it was just tough to think of him as the same character.
Overall a very good film and am looking forward to the next one.