Big Head Mode:

For the bikers to have larger heads, simply type "big heads" at the main menu.

Quick Recovery:

Press the [TAB] key to reset your player immediately on the bike to continue racing. This is extremely helpful if you're racing others and you fall. You don't have to wait for the cinematics of you falling or waste time getting back on the bike.

Rainbow Studios:

When playing, press [ALT]+[TAB]+[A] like you meant to switch screens. When you open up MCM2 again, the ground will be Rainbow Studios' pattern. To remove this, simply restart your race.

Hints:

Keeping your balance and adjusting the pitch of your bike while in the air is a key to Madness success. There are two ways to do this: you can either move your rider fore and aft, or you can work the gas and brakes to spin or stop that rear tire. Get comfortable with both and you'll find yourself crashing less and riding more.

As great as your bike and rider look up close, you'll want to pull the camera back quite a bit for a good look at the nearby surroundings and to ensure your entire bike is onscreen at all times.

There's more than one way through virtually every course, and sometimes it's not very obvious. Outdoors, you should explore through the foliage and memorize the results. Indoors, you can often set up your bike and modify your line to take an entire section of bumpy roadway in a single jump.