Preheat the oven to 350 F/176 C. Or heat to oven to the temp your cake recipe calls for.
Make the cake batter. For the cake mix, in a large bowl whisk together the eggs, water, and oil. Then add in the cake mix and whisk until the cake batter is smooth. If making the cake batter from scratch follow the instructions for that recipe. I have a few here on my website if you like.
Place the lego man cake mold on top of a sheet pan or cookie sheet. Spray it with cooking spray and then pour the batter into the mold roughly two thirds full. You will probably have some cake batter leftover which you can use for cupcakes or something if you like.
If the mold isn't laying level, place some folded aluminum foil under it so it is level. Then bake the cake for 25 to 30 minutes until a toothpick comes out clean.
Allow the cake to cool completely, then come in with a long knife like a bread knife and trim off any cake that rose above the mold. Don't worry if the cake split a little bit.
Now cover the cake in plastic wrap and freeze it for about an hour. You may get away with not freezing it, but sometimes, even when spraying the mold, it doesn't like to release the cake without breaking parts off, which we don't want. So for safety, it is a good idea to freeze it.
Next, gently remove the cake from the mold and place it on the cake board or cake pedestal. Time to decorate it. You may frost it with a thin layer of frosting first before doing the fondant, or just go straight to the fondant.
Take a chunk of yellow fondant and knead it in your hands until soft. Then roll it out until it is between 1/16th and 1/8th of an inch thick. Now place it on the head and use your fingers to smooth it around the head. Then trim the excess with a knife.
Repeat the steps for the hands, then use a different color for the shirt and pants. There are some special fondant decorating tools that are handy, but only worth it if you are doing to be decorating a lot of cakes with fondant.
For the face, use your finger to indent the eyes and mouth. Then fill it in with some black icing or make some pieces from black fondant and place them.
The lego man cake is now finished, enjoy! Cover it with plastic wrap and store at room temp for a couple of days, or place in the fridge for 4 to 5 days, or freeze it.