If you are a Star Wars fan, you're probably familiar with the scene where Han Solo is frozen in carbonite. We used this as the basis for our activity yesterday.
We took a couple of The Boy's Lego people and froze them in ice blocks.
Once we had our Lego men completely frozen within the ice blocks, we took them outside to free them. Everyone got a squirt gun, and they took turns spraying the blocks of ice to free the captives.