Alright to begin - I think we all know how to get under Orgimmar using the mount through walls glitch; if you don't, search for "under orgimmar" in exploits/exploration.
I'll make this short and sweet, so I'll only post 2 pictures though I think this is pretty self explanatory.
What I've found is that if you own a multi-passenger mount (ie. the chopper or travellers tundra mammoth etc), once you are under orgrimmar, mount directly west of the bank and anybody above ground will be able to jump into your mount through the ground.
Pics:
Also please don't reply with "This is common sense lolol ur retard." for obvious reasons.
Hope someone finds this useful/fun!