Featured on Equestria Daily: http://www.equestriadaily.com/2014/09/music-of-day-373_11.html

Normal Version: http://www.mediafire.com/download/wl3nifhs3usv95d/%5BMLP+x+Mario+Kart%5D+Lord+Tirek%27s+Grand+Prix+at+N64+Bowser%27s+Castle.mp3
Final Lap Version: http://www.mediafire.com/download/swucc1370kgmbi5/%5BMLP+x+Mario+Kart%5D+Lord+Tirek%27s+Grand+Prix+at+N64+Bowser%27s+Castle+FINAL+LAP.mp3

Twilight Sparkle and the princesses lost to Tirek in the race at Bowser's Castle because they were shrunken by his lightning bolt at the final lap. The four princess are captured, and the Mane 5 and Discord must challenge Tirek to a grand prix in order to save them. If one of the ponies or Discord takes first place, then Tirek will free them and give their alicorn magic back.

MLP by Hasbroo