Who is the protagonist in The Three Little Pigs?

Answer 1 (the moral lesson)

The smart, diligent, and hard-working third pig, whose brick house withstands the wolf.

Answer 2 (tongue in cheek)

The Big Bad Wolf, who is trying to control the rampant overpopulation of pigs, and to stop the destruction of natural habitats by brick-house-building pigs -- but who tragically fails.