This is just a simple fun thing to mess with passengers on your Grand Ice mammoth / tundra. When you get someone to get on your mammoth, they appear in the back on one of the seats. If you don't want anyone on your mammoth or just want them to miss out on buffs6): you can turn your mammoth away from a portal and back the people into the portal and make them zone out/in. If you do it right, you will not go through the portal and you will still be on your mammoth. Make sure you do it carefully, so you don't get ported out. Not to slow, because they might find out what your trying to do and just hop off.
I usually do this in OS or outside of RFC when I'm giving a nub a ride.