An example combat flow where this situation could occur:
- Player A trips Opponent B, AoO chaos ensues.
- Opponent B attempts to Stand Up, provoking an AoO.
- Player A uses an AoO on prone Opponent B, to perform a Trip attack.
- Opponent B provokes an AoO due to being Tripped (via Greater Trip)
- Once resolved, Opponent B provokes a further AoO from Player A (via Vicious Stomp)
I am aware that, once resolved, Opponent B would continue to Stand Up (presuming consciousness remains).
My question stems from having the ability to Trip a prone creature (due to there being no text saying you cannot Trip a prone creature), and how the Trip text specifies the result of tripping a creature:
You can attempt to trip your opponent in place of a melee attack. You can only trip an opponent who is no more than one size category larger than you. ... If your attack exceeds the target’s CMD, the target is knocked prone.