In Vanilla World of Warcraft playing as a hunter if you sent your pet to attack something and then used a flying route while your pet was on transit, it would mount you onto the flying mount but not put you on the flight path effectively making you invulnerable. You couldn’t attack while you were mounted and the mount didn’t fly but you could just waltz into the enemy capitals on an eagle before flying mounts existed ingame and watch everybody freak out and follow you around.