A sex act wherein when you're doing a girl from behind, you suddenly give her a charlie horse in the thigh as hard as you can, making her fall to the ground. Then you take a dump on the back of her head.
My girlfriend was screaming too loudly during sex and waking the neighbors, so I had to Charlie Brown her. We are no longer together.
The act of your lover taking a dump on your chest, and then taking two fingers and smearing the poop in a zig-zag pattern over your stomach like Charlie Brown's shirt.