I'd never heard of this cartoon (my kids are too big now) until I was asked to make Zach's birthday cake. I recommend it, it's lovely.
The cake is an 8" red velvet and the figures are made from sugar and entirely edible.
p..s I wouldn't recommend letting your kids eat them though as you'd be scraping them off the ceiling with the sugar rush. You could let the guests at the party eat them and let their parents worry about it, sure aren't they after having a couple of hours free time whilst you took care of their little one.