Madagascar Kartz

Load up the Zany Zoo Cup. You only race with four other people for a total of five racers. That means that you basically have to not get 4th or 5th. If you play on 50 CC this is obviously the easiest. You can choose whatever character works best for your playing style, but I've found that speed is usually the most effective for victory (Shrek). If you haven't unlocked Shrek yet, the hippo is a suitable replacement IMO. Simply complete all the races in 1st, 2nd, or 3rd, by doing well in all the races individually and collecting mangos accordingly (which are rewarded to you by winning, or can be collected along the race track).