Things you will need for this trick.
1 - Mechano-hog "I think it only works on a mechano-hog because of the magically appearing passenger seat, unlike the mammoths where the seats are always there"
1 - Orb of the Sin'dorei (sp?)
When you have a passenger use your Orb, proceed to have lots of lulz
WARNING - backing up while your passenger is upside down may cause skid marks on his balls