Cake Dimensions

We were talking to Oblivia about a cake that she was making for a friends birthday. Oblivia proceeds to provide details about how great the cake was going to be. It was white with purple frosting and had sparkles... sounded really great. Then she started to describe how large the cake was: "It's a round 18-inch cake that's 2-dimensional...", confused by the comment, I asked, "Oh, do you mean it's 3-dimensional?", she responds, "No! It's a 2-dimensional cake!", okay.... *ignore the comment*

She then starts describing this cake that she had made last year for her friend's daughter's birthday, "She wanted a pumpkin cake, so what I did was I got two baseball forms and stuck them together to make the pumpkin, so it was like a 4-dimensional cake..."

First off, is it really necessary to specify the dimensions of a cake? I mean isn't it safe to assume most things are 3-dimensional... just saying... Also, what exactly would the fourth dimension be? It's the special time travelling cake! New and improved! Finally, why was the first cake 2-dimensional and the other one 4-dimensional? Well clearly if the first cake is 2-dimensional and for the second cake she had to use two 2-dimensional cakes to make it, then two plus two equals four. Voila! You have a 4-dimensional cake...