aight. here's what you do.
grab some tube steel and a ball reciever that fits the ball on the rear bumper of your truck, and weld it all together. next, take all of the washing machine apart, remove the motors and everything else, as well as the drum, but leave the mechanism in it that allows it to turn. rip the agitator (sp?) out of the drum, and replace it. next, find some heavy duty rubber utility wheels, (go steal some wheelbarrows) and make an axle. make a frame for these that'll bolt onto the front (or back or side or bottom) of the body. bolt them to the body and make some steel brackets that the washing machine can attach to the welded tow bar. throw one of those cheap locking brackets onto the lid and the side (underneath so you hafta get in to put them on), rivets work best, or if you can weld good, do that. zap it up, give your buddy some football equipment (full faced helmet is a MUST) and a padlock and key and tell him to get in and lock it. back your truck up, and attach the whole contraption. drive down the highway at 100 kliometres per hour, or just bugger around in the fields beside it. for an extra scare, give him a lexan window to look through, just by welding up and riveting a bracket to whichever side you feel will scare him the best. REMEMBER. BE SAFE. TRY NOT TO DO ANYTHING THAT WILL ENDANGER HIM MORE THAN HE ALREADY IS. PUT VENTS ON THE OUTSIDE SO HE DOSEN'T GET GASSED FROM THE EXHAUST FUMES. THAT WOULD REALLY, REALLY SUCK.
i am a pro, i've done this more than 20 times. if you need any help just pm me. i'll tell you all you need to know.
enjoy.