It's a classic Hollywood maneuver, a couple embrace in a kiss and the woman's leg bends at the knee and rises. A visual metaphor for arousal and erection. It's also an excellent example of what Freud referred to as "predicate thinking", the treating of dissimilar objects as equal when they share physical attributes, common in the primary process thinking of dreams.
Madonna with her own less subtle metaphorical erection.
A Bath and Bodyworks promotional coupon for a new product called "Dark Kiss" featuring a cosmetic photography cliche, the o-face.