My son turned three and wanted a Homemade Spongebob and Friends Cake with all his favorite characters. All of the characters are colored gum paste. I always do the arms and legs separate and add spaghetti noodles (since you should use all edible ingredients) in immediately after molding them.
I poke holes in the bodies with a noodle as well so when the arms and legs are dry I can attach them together. I use a gum paste and water mixture as my glue. I will use a boxed cake sometimes if I don’t have to stack cakes really high so I just use extra egg and butter to make it denser like a sponge cake.
For the pineapple house I cut out three circles, each one gradually smaller. The cake was coconut with a pineapple coconut filling. I used instant coconut pudding and a small can of crushed pineapple. I purchased whipped frosting from Walmart and used for the coating before applying the fondant. This type of frosting is not recommended for stacking or using under fondant. However, I feel that it binds the cake together well when used cold.
I also use a homemade marshmallow fondant which is not as heavy as the premade kind, so it works well together and tastes great! The Krabby patty cake is a vanilla butter cake with white butter cream frosting and marshmallow fondant. I used two ten inch cake pans. I also colored royal frosting for the burger, ketchup, mustard, and lettuce.
I used Easter egg sprinkles for the sesame seeds on top. The rock house was sculpted out of homemade chocolate sponge cake and filled with a chocolate mousse and chocolate butter cream.