First, I am always surprised at Japanese culture's tolerance for the word poop. There are comic characters and even little ornaments designed in the shape of poop, and I have to admit that they are cute.
It is clever to link the nuclear explosion to something happens in people's daily life and can be easily understand by children. Although it is less in seriousness, it indeed helped children to get a general understanding of the explosion.
The animation, character, sound, color and background image used in Genpatsu-kun are livelier than in Nuclear boy, which could be better for attract children's attention. The Japanese version should a strong attention toward restore people's confidence while the English version's tone is more neutral.
