Based on this post for a mod of Civilizations IV: Beyond the Sword:
http://forums.civfanatics.com/showthread.php?t=249675Let's see if we can get this list all the way too 1000!
1. You hear an airplane fly by and shout "The Drengen are here! The Drengen are here!"
2. When you do the above, you get your plasma blaster and shoot it down
I'll post more later, now let's see your creative juices flow!