Incrementing/Randomised Array?

Hey guys,
I just wanted to babble around some ways to make the following NPC system work. My non-player characters in the game can be clicked, and when someone does they spout out annoying useless information. Sometimes, completely randomly, they’ll say something you actually can use.

I’ve already set up a simple system where text is pulled from an array and displayed, and I set it up so it starts at 0 and goes through till the end of the array’s length. I can loop it easy enough (I’m solving the ‘make it re-usable’ problem as we speak!) but my next step is to make it occasionally spout out goodies. And I mean like, occasionally .

Anyone got any good ideas?