A mr brown hand is when you take a shit directly into your cupped hand. Then proceed to smear the fecal matter onto/into someones face (preferably near the mouth). This should be done while the person is asleep or past-out from the consumption of alcohol or other drugs.
Man you should have seen the Mr Brown Hand we gave Charles last night. When he woke up and realized that there was shit all over his face and in his mouth he just about tore the house down.
Woody made Alex so angry for ignoring his phone calls and being such a douche that he shit on his front porch and wiped some of it on the door handle in an attempt to get back at him, thus giving him a brown handle.