A slew of these things were released in the mid-to-late part of the decade. After striking the bottom of the figure against a hard surface a few times the toys would speed away on a little rubber wheel spitting sparks out of a opening in their mouths, or in the chest as was the case with the Ultraman figure shown here. Some of them worked better than others. I was never able to make Ultraman travel very far before it toppled over on it's face with a screech. The best sparkies were definitely King Ghidora and Mechagodzilla thanks to their colorful shiny appearance.
I really don't know exactly how many of these were released, at least during the original time frame I'm discussing here. I've seen sparkies of Gamera and Daimajin but was never able to purchase them. Additionally, these little toys have been reissued several times over the years, usually as keychains. The Minya shown above was actually attached to a keychain, which was easily removed. Sparkies based on several of the Gamera kaiju were also made available recently, some cast in clear plastic in order make the inner sparking mechanism visible. There could be many, many more of these available that I'm not aware of, so any and all information would be helpful.
Lastly, it's interesting to note that the Baragon, Angilas and brown Mechagodzilla shown above are actually bootlegs, and are of much poorer quality than the legit Takara figures. The licensing information has been removed from the bottom of the toys and the sparking mechanism was obviously done on the cheap and would break easily. None of the three figures above work properly anymore.
For a Godzilla fan in the 1980s the severe lack of available toys was frustrating. That could be why these little sparkies were so cool. They'd be no big deal today but for the time they were really fun little toys. Spark on, little kaiju!
