Trample
As a full-round action, a creature with the trample ability can attempt to overrun any creature that is at least one size category Smaller than itself. This works just like the overrun combat maneuver, but the trampling creature does not need to make a check, it merely has to move over opponents in its path.
Can you make an overrun check if you want to knock the creatures prone?
If you have improved overrun and you knock the creatures prone, can you take an Aoo?