I'm pretty sure that they are based on the KA-S and the KA-P. I own the KA-P and it looked a lot like a watermelon I saw at my local uke store the other day. Prices are comparable as well.
Just checked on the website. The Ukadelics all start with "KA-S", as in, KA-STIKI, so it must be the KA-S with decor. The pineapple decorated one is KA-PSS, but the Kiwi and Watermelon ones have KA-KIWI and KA-WTML. They are around the same price point, so I would guess they are a KA-P decorated body with different headstocks.