Get Mystery Rider:
To get Mystery Rider beat all the tracks on easy mode then he will sometimes be choosable.P.S the Mystery Rider is Plankton from the T.V. show Spongebob Squarepants.

Hidden Racers:
If you beat the game 3 times you can get 5 new racers.You can get Phli and Lil from the rugrats,Sid from Hey Arnold,Doug from Doug,and Otto from Rocket Power.

Turbo Boost:
At the beginning of a race, when it's on 3, hold down the up button on your keyboard and you should get a boost.

Shortcuts:
On the Reptar Raceway, start off and after the first turn take a sharp right then there will be a cave go through there and it will save you a few seconds. On the second race in the second cup (I forgot what the name of the track is) When you go into the tunnel and a sign above you says COLISEUM take a sharp right and you will go through the real coliseum and this shortcut saves you about seven seconds. In the last race in the third cup (I forgot the name) when the first intersection comes take the left. Then drop off the first jump and the entrance to the top volcano level is there. You can also try the second jump I've never tried it yet. Unfortunately, These are all the shortcuts I know.