They're little cardboard trading cards. The most common are tiny one-by-three inch rectangles, but they come in all sorts of shapes and sizes: circles, squares, you name it. If you've got a favorite anime or tokusatsu character, chances are there's a menko for it. They were produced in massive quantities throughout the 50's, '60s, and '70s, though collectible card games like Pokemon have eaten into the action lately. At their most sublime, they're art. Like pocket-sized woodblock prints. Hokusai, eat your heart out.
There's about ten zillion types of menko out there, but my favorites are the ones featuring foreign characters. Like this guy, who I don't recall having seen in Ultraman.
Or having fought alongside Oba-Q.
Is that Johnny Weissmuller? I pray there's a "Greystoke" version with Christopher Lambert, too. Love the yawning elephant.
Have you seen these men?
My all-time favorite: The Horribly Malformed Extraterrestrial. How much better would ET have been if it'd starred this stoner instead of Elliot?