Swingin' Thumbs!

In the early console era, thumb-based controllers were not yet common; most players would fumble for a while when the Nintendo NES arrived a few years later, learning to maneuver and press multiple buttons with the opposable digits previously employed for simple grasping and squeezing.

One pioneering exception was Nintendo's Game & Watch series.  An American company imported and distributed similar handhelds produced by Masudaya, and decided to emphasize the control approach by calling itself Thumb Power:

I like the artwork, because these thumbs aren't just having fun -- they seem to be indulging in some kind of over-the-top 70's swingers' party orgy.  There certainly are a lot of goofy grins, googly eyes and tongues hanging out, at any rate, with the mass of thumbs positioned carefully to avoid revealing any naughty knuckle bits.  We see red and purple nail polish wherever we look.  And at bottom, there are even a couple going at it in the kitchen.

Hans Brinker would be dancing in his grave.