We had a 3 hour blackout the other day. Joshua had been in his basement playroom when, suddenly, the lights and his ABC movie turned off at the same time.
He was very startled and didn't understand why nothing worked. He wanted a drink, but I told him we couldn't open the fridge (at this time, we didn't know how long the blackout would be). He started crying, asking how we were going to get food.
I calmed him down, and we made powdered lemonade. He got a cup of Goldfish crackers. Then we set to work and built a fort for him in the dining room where he could snack and color until the power came on.
The power came on just before bed time, but the fort stayed another few days. Every time someone came over, he would tell them to come and see what Mommy built during the blackout.