My kid and I made some custom Miis on the Wii after finding a site (https://MiiCharacters.com) that has a database of custom ones and step by step instructions on how to make them. I found (and my kid made) the David Letterman one, because I thought that would be amazing, to be able to race karts and motorcycles as David Letterman. 
In Mario Kart, there's a thing where you can race as the same character. My son and I noticed that when you both race as Daisy with bikes and you both place, it randomly assigns a head to one of your characters so they won't both be the same.
So that's how Dave in Daisy's lovely yellow dress happened. A hilarious result. 
