This happed to me on the last race of the last cup I had to do to get the gold kart. I got first place on the first three races then N64 Rainbow Road comes around and I'm out in front for pretty much the entire race. Then I get to the last corner and along comes a blue shell. But oh wait! whats this? A red shell also? why thank you sir...and whats this? Mario overtaking me at the last second to put me down yet another place? By then end I wound up in 7th. I didn't get my star...I raged...I raged harder than I have ever raged before. THEY TOOK MY GOLD KART FROM ME!!!
I got the gold kart eventually, allong with the gold wheels. So Its not so bad, might upload the video of the replay later. It was complete fuckery. Complete and utter fuckery.