Have you ever played with a yo-yo balloon? I remember playing with them as a child. They were really popular at craft shows and art fairs as a fundraiser. My kids got some last year at my nieces Christmas concert and absolutely loved them. We made some ourselves in honor or National Yo-Yo Day. They're so easy to make and so much fun to play with.
Fill a balloon with water until it's about the size of a golf ball.
Blow it up with air until it's the size of a pear (or orange, if your balloons are rounder than ours) and tie it closed.
Don't be alarmed if your balloons and rubber bands change colors. It's all just part of the magic.
I laugh every time I watch this.