Bake a standard cake recipe, either a box cake mix or your favorite homemade cake recipe in a 10-inch round cake pan or 9x13 pan. I have several you can use here on this website. Allow the cake to cool completely.
Search google images for a Detective Pikachu face to use as a template or you can use this one. Cut around the template removing the excess paper. Cut off the ears and hat and save those for later.
Put the cake on a cake board. Then place your template on top of the cake and cut around it with a knife. Save the leftover cake bits, we will use these for the ears.
Time to trim the tail, so it isn't so fat. Cut halfway down into the cake using the template as a guide. Then cut it horizontally to essentially make the tail half as thick.
Next, place the paper ear pieces on some cake scraps and cut those out with a knife and place them on the cake board.
Now frost the whole cake with your choice of frosting. The frosting will help glue the ears in place.
Take a large chunk of yellow fondant and knead it until soft. Then roll it out to it is at least a few inches larger than the cake on all sides, and about 1/8th of an inch thick. Place the fondant over the cake and smooth around it with a smoother or your clean hands, to form it to the cake. Trim the excess at the bottom of with a knife.
Define the feet a little better by indenting the fondant with a fondant tool, or a handle of a butter knife. Do the same with the chin. This isn't necessary but it adds depth and detail. Run the knife gently over the feet to resemble toes.
Grab some more yellow fondant and form the arms, use the template as a guide. Place them on the cake, use a bit of water as glue.
Roll out some black fondant and cover the ear tips. Place a dab of water where the nose will go, then form a little tiny triangle shape from the black fondant and place it where the nose should go.Then using a toothpick and a bit of water draw an outline where the mouth should go. Take a tiny piece of black fondant, roll it out and then place it for the mouth.
Now use a piping tip to cut out round pupils out of the black fondant.
Next, take some red fondant and knead it a bit in your hands. Then roll it out really thin and using the bigger end of your piping tip cut out two cheek circles. Then place them on the cake, again using water if needed to get it to stick.
If you didn't buy brown fondant, you need to make some with white fondant and a bit of brown icing color. Take a toothpick and dip it into the icing color and then put it onto the white fondant. Then knead in the color, repeat until you get the desired brown, or for course you can skip this step if you bought brown fondant.Roll a little bit of brown fondant out then using the same piping tip you used for the cheeks, cut out two brown eyes. Then place them on the cake. Next place your black pupils. Then place two small white specs for the eyeball highlight.
Now grab a small ball of brown fondant and shape it into his had. Set it on his head. Then make a little ball of brown fondant and put it on the hat to complete the detective look. You are finished! Enjoy!