Here is an example for Oh no... INVASION!!! the cooperative card game.
You see player two in trouble. The red Invaliens (top left) that are flying by will give attack orders to all yellow Invaliens in play (the attack order is in a yellow balloon) as soon as they invade somewhere (card is placed). Some one will have to ZAP the card and make sure they do not get to land or player two is done for!
See fablesmith.com or BGG for the full rules.