I got the Character Kit to go along with my Zoku Duo, and it is AWESOME. The possibilities are seriously endless. You can create tons of faces. It's super fun for me, an adult, and I can only imagine how much fun it will be for future children.
I love how easy it is to make the faces, but it can be kind of difficult getting them to stick inside the unit. Even after dunking them in water as suggested, I still had a few slide around and a couple that fell off and had to be repositioned. I think even with that, it's still a 5 star product, though. It's not a huge deal to me, but might be to others, so keep that in mind.
I think this is an excellent addition to any Zoku quick pop maker.