We have a list of shy guy AR codes for multiple games. Refer to the AR manual for installation.

Mario Kart DS

Always shy guy...

Pink:
023cdd40 0000000c
023d99dc 00000006

Red:
023cdd40 0000000c
023d99dc 00000003

Yellow:
023cdd40 0000000c
023d99dc 00000002

Green:
023cdd40 0000000c
023d99dc 00000000

Light Blue:
023cdd40 0000000c
023d99dc 00000005


Dark Blue:
023cdd40 0000000c
023d99dc 00000001

Snifit (kind of):
023cdd40 0000000c
023d99dc 00000010

Black:
023cdd40 0000000c
023d99dc 00000004

White (may be offensive to some people):
023cdd40 0000000c
023d99dc 00000007

Shy Guy silhouette:
023cdd40 0000000c
023d99dc 00000009

ONLY USE ONE AT A TIME!!! If you want to change colors you must restart the DS, DESELECT the previous color and choose a new one.
Note: If you pause the game and press the "Change Characters" button or "Change course" button then press the back button the game will freeze.