Henry Wadsworth Longfellow was an American poet who, as it happens, has a frighteningly appropriate last name.

Sirius can a little caught up in his own brilliance at times, I think. Things come easily to Sirius which is why he and James were at the top of their class without really working that hard at it. It doesn't really occur to him that this might not be true of poetry as well.

He has sex on the brain when he's writing it, obviously, and gets a little carried away. A very human thing to do.

Trust me, as bad as you think that poem was, it was worse. Sirius doesn't things in half measures and this is no exception.