Speed Boost
To get a speed boost in Konami Krazy Racers, press the A button down the exact same time the 4th head glows when you are starting the race. If you do it correctly, you will start with significantly more speed.

Unlock Bear
Bear is a secret character hidden within one of the courses in the game. To get him, begin a race (not a free race, an actual competition) on Cyber Field 2. As you approach the finish line, grab the blue diamond that sits between the two gaps. Complete the race and save, and Bear will be available on the Character Selection screen.

Unlock King
King is a secret character hidden within the Sky Bridge 2 course. To get him, begin a race (not a free race, an actual competition) on Sky Bridge 2. Grab the Blue Bell and use it to to make a blind leap to the right at the first large gap, landing on a distant platform. Here, you'll find the blue diamond. Grab it, finish the race, and save. King will now be available on the Character
Selection screen.

Unlock Vic Viper
Vic Viper is a secret character hidden within the Moon Road course. To get him, begin a race (not a free race, an actual competition) on the Moon Road. At the first long gap, use a boost to make a blind jump to the right (instead of going straight over the gap). Land on a long platform with the blue diamond on it. Once you collect it, finish the race and save the game. Vic Viper will now be selectable on the Character Selection screen