Konami Krazy Racers

Bear:
Start a race on the Cyber Field 2 track. Collect the blue diamond between the two holes near the finish line. Complete the race and save the game. Bear will be unlocked on the character selection screen.

Ebisumaru:
Unlock Bear. Play the Ganbare Dochu 1 and 2 tracks with Bear and beat the record time to unlock Ebisumaru.
Information in this section was contributed by sean_magana.

King:
Start a race on the Sky Bridge 2 track. Collect the Blue Bell power-up, then find the jump just before the large gap. Note the blue diamond on a platform just to the right of the jump. Jump towards the platform, using the power-up for an extra boost. Collect the blue diamond, complete the race, and save the game. King will be unlocked on the character selection screen.

Vic Viper:
Start a race on the Moon Road track. Collect the Blue Bell power-up, then find the first long jump on the track. Jump and use the power-up for an extra boost to land on a long platform that has the blue diamond. Collect the blue diamond, complete the race, and save the game. Vic Viper will be unlocked on the character selection screen.

Hint: Quick start:
Accelerate at the moment when the third light dims and fourth light illuminates.

Hint: Magma Castle 1: Shortcut:
Cross the first two bridges and the first dirt path. On the second dirt path, instead of making a right to continue, go to the far left and you will find a jump that leads to another dirt path. Jump off the three small jumps, then make a sharp left turn. The finish line will be a few inches away from you.
Information in this section was contributed by ZeldaFreak0103.

Hint: Control replay:
Finish a race in one of the top three positions. Hold B after your race time disappears, then use the D-pad to change the view.
Information in this section was contributed by Max Leblanc.