It's often the case that the simple things in life are the best—and that goes with pranks too. Forget about your elaborate, drawn-out practical jokes because this has it all, including the victim's hilariously feeble cries of despair.
And all it involves is a bottle of shampoo. A bottle of shampoo that's constantly applied to a guy's hair as he's showering, tricking him into thinking the soapsuds are never going to disappear and he'll be rinsing his hair for all eternity.
"IT'S NOT COMING OFF" he screams. "COME HELP ME!"