Here we have the first option: After finding out that you have misfiled $20 of your allowance, you rush to Target to buy... anything! You want a specific Barbie, after discovering no store within 10 miles carries it, you quickly shift to wanting anything- just as long as you spend $20. You even offer to buy Pokemon cards just to get rid of the money. After several heart to hearts with your mother you settle on a Barbie pool and a jeep to drive them there. Cost: $20.
This is the second option. You spot your sisters new Barbie pool with real water! You circle around her for a couple of minutes and then you make your move. You tap your finger in the water a few times and she tells you to go away. Then inspiration strikes, you run to the kitchen, grab a spoon and begin stirring the pool Barbie and all. Your sister goes into hysterics causing your mom to dig out old tupperware and a few plastic toys thus providing you with your own "pool."
Cost- Free. Added bonus- Your sister in hysterics can be very entertaining.