The company which releases these is called Wyncor. The balls contain a plushie, which expands when you open the ball.
They also produce little bags which can be decorated/customized with a lot of stuff. So far no ponies, but as they have the license, maybe we will get these too. It looks like fun. And a money sink if you have to buy all those different packs with the decorations
Wow that was a pretty impressive stall for Nebulous Stars they have such pretty art but I had no idea they were popular enough to have a space that big