NINJA BOY CODES
SYSTEM: GAME BOY/GAME BOY POCKET
COPYRIGHT 2000 THRASHNET GROUND ZERO SIX PRODUCTIONS ALL RIGHTS RESERVED
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STAGE SELECT
On the title screen press the following:
UP, UP, DOWN, DOWN, A, B, A, B
Then press and hold the following:
A
Then press the following:
START

CONTINUE
After you lose your last life and the Game Over screen appears press and 
hold the following:
A
Then press:
START
You'll continue from the last stage you were on.

    Source: geocities.com/tgz6/codes/Game_Boy_Pocket_BW

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