Doritos Crash Course 2 - Officially Licensed Achievement Guide
43First, you'll need to unlock and equip a FameStar costume. To unlock a costume, you will need to gain a total of 500 FameStar Points by completing FameStar Challenges. All these things can be seen by selecting "Avatar FameStar" from the main menu.
Once you have a CC2 Costume equipped, you'll need to go the the shop, and purchase and/or equip some jinxes. To do this, you'll want to go to the "Jinxes" tab, then purchase some and equip it with Y, and you'll see a small icon under your character.
Now, you'll need to go into an online game with other people. Wait until the match begins, and once the race starts, just wait for a second or two after the other players start racing and press B. Pressing B will jinx a player in front of you, and you will unlock the achievement!