I'll be honest and say that I don't know what "Pakkana" means, but I'd guess that it's an onomatopoeia for the sound of something shaking in a box. I could be wrong, and I'm guessing that, if I am, the language-philes out there will pounce on me and let me know my grotesque inadequacy in no uncertain terms.
Images from Nestle Japan's site.
Nestle Japan created a series of three boxes with 20 mini KitKats. There are 10 milk chocolate (regular) KitKats and 10 "adult sweetness" (semi-sweet chocolate) mini bars. The first is a "circus" box which you shake lightly in order to get the clown to appear. According to the blurb, this is to help you enjoy the circus along with the KitKat. This seems like it would appealr to the type of people who are easily distracted by shiny objects.
The second design is a "cracker" design, and I don't mean the salted dry snacks that we enjoy spreading peanut butter on or garnishing with slabs of cheese. This is in the sense of a Christmas cracker. They claim in their blurb that having this on hand will enhance the image of a fun and lively party, if you're having a party.
The final design is targeted toward sophisticates who think that boxes of KitKats can make attractive decorative pieces in their homes. This is called the "piano black" design and they encourage you to place it on your kitchen counter or in your office to impress people with your refined sensibilities. Of course, if you're that pretentious, I think you'd be better off parking a box of Godiva chocolates on your counter instead of KitKat minis.
These are on sale for 630 yen ($7.91) per box and were introduced at the beginning of March while I was still living in Japan. However, I never saw them on sale anywhere and was around for about 3 weeks of their release. The web site does say that their availability is limited so you may have to look around a bit if you're a collector and just want the boxes. If you just want the candy, you can find the adult sweetness and regular bars anywhere and everywhere.