Why so serious?

My father was...a drinker, and one night when he was especially crazy. My mother grabbed a kitchen knife, and daddy didn't like that. No, not at all. He took the knife, and started cutting up her face, laughing the whole time. After he's done, he looks at me and says, "Why so Serious?" He comes over to me, puts the knife in my mouth, and tells me, "Lets put a smile on that face!"