I made all the decorations on the Spongebob Scene Birthday Cake in advance. The pineapple, SpongeBob and Patrick are shaped from chocolate rice crispy treat, and then covered in fondant. Patrick took a couple of layers of fondant and then gum paste to get a smooth look.
I painted the pineapple with yellow, orange and brown food coloring and pearl dust, and then drew the lines with brown food coloring marker. The door and windows are made of fondant and colored with blue food coloring and pearl dust, and then I drew on them with food coloring markers.
I colored SpongeBob with food coloring markers and drew on his face; I used bamboo sticks for his legs and arms. Patrick has a pink colored gum paste exterior and swim trunks, I drew on his face with the markers. Plankton is made of fondant, colored with markers, has stamen for arms and Gary is also made of fondant, toothpicks holding up his eyeballs, and colored with the food coloring markers.
The flags are bamboo sticks and construction paper. The green stepping stones are painted with green food color and petal dust and the party hats are made of gum paste and colored with markers. The sand is 'coco/vanilla puffs' cereal that sat in the food processor for a while, the walkway and water are writing gel. I baked 2 layers 9 x 11 yellow cake, filled it with chocolate ganache and whipped cream with sliced bananas and strawberries and covered the whole cake with whipped cream then the crushed cereal, gel, and fondant figurines and pineapple house. I cut pieces of my palm tree and covered the stems with tape, carved a hole on top with a pumpkin carver and fluffed out the stems and pasted them down with a wad of green gum paste.
The cake was a hit and all the kids were asking: how'd you make that, what's it made of, can I eat it?