Turning to the Internet for various ideas/copyright violations, I got an idea from Happy Birdycake and made some Ponyo puppets to put in little buckets as a party favor. After that was figured out, the rest of it sort of fell into place ... a bit of construction paper, a lot of streamers, construction paper for Ponyo's sisters ... and the requested ice cream cake (non-Ponyo). C40 was tasked with figuring out party games; he managed to find one decent one (jellyfish jump), but M6, G5, and B6 helped think up a few other uses for the hula hoops and giant purple ball, keeping the kids occupied.
The ice-cream cake proved a big hit, not so much for the store-combined layers of vanilla ice cream and chocolate cake, but for the blue icing which had some ... interesting effects.
And so, without further ado, here are the pictures: