From Glue to Mon Dieu!

"During a Grand Prix, finish a race in first after placing last in the previous race."

An obvious way to get this is to intentionally lose a race then come in first in the next one. This is easier to do the fewer people there are. On the game where you intend to win, you may want to hang behind the other people for a while until you get your weapons.

If you have somebody to boost this from, it is insanely easy. Just win, let them win, then win again and you should both have it.