My favorite sex position is the JFK:
I splatter all over her as she screams and tries to get out of the car.
Listen up, buttercup. This joke is dark, like your chances of understanding it. The joke refers to JFK, that is John F. Kennedy, who was shot in a car. The joke is that the poster is having sex in a car, splattering on his partner, implying that the partner is dead, like Kennedy.