Looking for a recipe for a "Walmart Cake"

I got a cake from Walmart a few years ago and I don't know how else to describe that kind of cake. It's the kind you can get for birthday parties, decorated with things like current kids movies. I had it with KungFu Panda deco when I got it.

I assume that it's some kind of vanilla sheet cake, but I can't find what kind of icing it might have been. It's pretty much just pure sugar, with really thick icing all over, the kind that you'd also see in the shape of flowers on other cakes. I don't think it's butter cream, though it looks similar.

Any ideas? Thanks!

bon appetit