Mario kart DS Semi Shortcut found! :)

[Shujinco2]

On Rainbow Road, when you are going up the loop, start drifting to the right. Have it so your facing between the way your going and exactly right of you. (In other words, turn 45 degrees.) Then, when your going straight up, have your back tire hit the left railing. You should jump through the entire Loop and end up on the other side of it. :)

[GreatGonzales106]

Cool, I'll try that out sometime.

[B9M]

Cool find :) -- I'll have to try that sometime, once I get a new battery for my DS.

[Shujinco2]

It's very hard. You have to hit it in the right place at the right angle. :-\