The Original Pin
First, the block shape. The instructions have you cut the top of the cake off so that it is completely flat. This will help tremendously!
Next, the frosting. The instructions have you frost the cake, then freeze it, and frost again while the cake is frozen to seal in the crumbs. I know, if you are like me you don't want to take the time. If you are particular about the look though, you'll want to do a crumb coat.
Third, the lego studs. I almost called them posts, but I didn't know if that's what they were really called, so I had to go look it up. The sticky-uppy parts of the Lego blocks are called studs (did you know the machines that make Lego's have a precision tolerance of 2 micrometers...they have to get things pretty precise to ensure the blocks all fit together properly). Now that you have that piece of trivia to share around the dinner table, I'll proceed. The studs in the original pin were created by cutting large marshmallows in half and frosting them. My thoughts were, "Why not just use mini cupcakes. Those look like the right shape and size." And it looks like maybe that was Lou's thoughts as well (or maybe I'm seeing crumbs from the actual cake stuck on the frosting...not sure). As I think about it though, marshmallows will give a more accurate shape and they might be easier than cupcakes.
Fourth, the coloring. This recipe called for the pre-colored gel frosting, which is already vibrant and ready to use. If you don't want to use that, and want to color your own, you need to use cake/frosting specific colorings. The normal food color many people have in their cupboard just won't cut it (and will change the texture of your frosting...learned that one the hard way).
So there you have it! Lego cake! If I had some of that on hand, I think that'd be my breakfast. You can't go wrong with cake, frosting and marshmallows!