Mystery Plant

This plant is an "invader; an encroacher" (quote from "Beauty and the Beast" one of my favorite Disney movies, for all you Disney fans.)

It came under my fence last year from my neighbor's yard. I liked the leaf and thought it might be ranunculus, so I let it be. This year it has grown considerably and has bloomed. I really like the spiky, white flower--not at all what I expected it to look like.

My neighbor has no idea what this plant is called, nor can she remember planting it.

So, here's the question of the day--does anyone know the name of this plant?

Related Tags: plants, volunteer plant, ranunculus, Beauty and the Beast, Disney, quote