Read enough fractured fairytales and one realizes: the wolf is the most attractive character.
So much so that in some renditions, the wolf tells the story.
Why?
One obvious reason is that the wolf is a rogue and rogues are attractive (see Yul Brynner) but I think another reason is the reason Spike & Crowley were so useful to writers within those franchises: the wolf is the objective, wry outsider who can tell us things.
Wolf narrators are Jane Austen, raising their brows at the foibles of others. Whenever we want a break from angst, we go to the wolf.
In Into the Woods, Broadway version, the wolf also plays Cinderella's prince. The Cinderella prince is less romantic than his brother. More crafty and cunning. Like Dracula and Lucifer, he mixes truth with falsehood. He is an ambiguous antagonist who requires an equally cunning protagonist--or a ruthless innocent like Castiel.
Also, the wolf looks good in nineteenth-century dress.
