The Dendy is a Russian NES, which was released there with 100-in-1 cartridges, showing out to be counterfeit as Nintendo did not localize there. I don't think anyone did during that time.
Anyway, the Dendy looks like a Famicom, is very fragile, hard to find, and the games are texture hacks usually. All of the games released are NOT known, but Super Mario Bros and Tetris were very popular while being released on the "super-cartridges".
So, to avoid any other problems, I'll just lock this up. Most information is hard to come by, so be lucky that this is here.