If you activate Koopa the Quick's text when you are far enough away, you can start the race while he is invisible. If you do this, then he will be stuck in his starting spot invisible, and he will never finish the race, so you will never get the star. So if you finish the race in 0 seconds, he will not give you the star.
![](https://i.ytimg.com/vi/iuL46B5Uzec/maxresdefault.jpg)