Mirror mode on Nintendo WFC depends on the points every player in the V.S race has. For example: if there is a race full of players that only have 5000 points, mirror mode will probably not show up. But if there is a race full of 8000+ players, mirror mode is more likely to show up.
It's kind of how people play Mario Kart wii , if you play it REALLY well, you would think mirror mode is really easy.So it depends on how you play.
You unlock Dry Bowser
Mirror mode only comes in 150cc.
you have to get at least one star in all mirror mode cups
You need to win gold trophies in every cup on every mode.
Well on the Wii you have to get a gold cup in every course thingy then you will get it.
All you have to do is to beat the Lightning Cup in Mirror Mode. To unlock Mirror Mode you have to beat all the 150cc cups.
You have to Unlock it by Winning all 150cc Cups. Does that help? Good!
Get gold Cups on all the 150cc Grand Prix races.
the only other way would be too cheat
its were everything is reversed like a mirror
For Mario kart wii attain at least one star ranking in all mirror mode cups. For ds you can't and any other console I don't know. :)