[Shea]

Some of you have most likely seen ice crack and sometimes pop out of your drink. 

What the heck causes that???

Where does the force for that come from?

My guess, stemming from my extensive lack of experience in nearly all scientific fields, is that it has something to do with gases that get trapped in the ice.  Sometimes, during the freezing process, when you take the ice out to see if its frozen yet, it cracks, and you see bubbles under the surface of the ice.  I think that somehow that gas is behind the mysterious ice popping phenomenon.

[Mitch]

Never seen that. Can you try to duplicate the process and post your results here.

[Shea]

Yeah, it's happened to me a few times. One time it's even broken the glass I was using. However, I don't have the slightest idea as to what conditions I'd have to recreate, because the environment outside the cup is surely as much a factor for the possibility of an, "ice pop," as the environment inside the cup.  Also, the size of the cup, and the positioning of the ice inside the cup, and whether or not the ice has stuck together such a way to allow an ice pop, are all factors.

I wouldn't know how to get the ice to pop again.

[ATMyller]

The cracking is quite common I've fitnessed it several times. Usually with large, unsymmetrical and very cold pieces of ice e.g. a block of ice just taken from fridge and chipped with icepick.
Most likely the sudden temperature elevation causes thermal expansion (or more like thermal shrinkage in case of the ice) which creates mechanical tension and causes the cracks. The blocks sometimes even break apart.

But I've never managed to get the ice pop out of the drink.

ooh 100th post.