How do I pick random object?

I need to pick an random object. Example:We had 3 cubes, one of them, picked by random, is sizing up. How to do this?

There is 'system pick a random instance' which will pick a random cube if it is instances of the same object. If you are talking about 3 different objects then you could give them instance variable with an ID, number them. Then use choose(1,2,3) to pick randomly either 1, 2 or 3 and they relate to the object with that number set.