In Canada, 1998 there was a promotion with special packs of Wrigley's Hubba Bubba bubble gum to send away for free exclusive Crazy Bone figures. All you had to do was send 3 Hubba Bubba wrappers to the Crazy Bone's mailing address and they would send you the exclusive figures. However! The promotion was short lived (expired January, 31st, 2000), and as it wasn't promoted properly, the figures never were popular.
Not much information is known. There were 20 characters in the series. There is probably only about 500 figures in existence. They are very rare.