Sex Tetris by Sergey Tkachev and Oleg Kudinski (ZX, 1993)

What is it?: A Tetris clone with (more or less) erotic graphics, 1993, Sinclair ZX Spectrum.
What computer or emulator will it run on?: N/A.
Tags: Erotic Tetris.

This game by Sergey Tkachev (game code) and Oleg Kudinski (disk loader code) may well have served as the inspiration for XTet (which, incidentally, is probably what you were actually looking for, if you arrived here from a search engine), but it is not a direct ancestor. While the graphics are similar, the gameplay is still that of conventional Tetris. Unfortunately, the well is rather low, and the game is therefore rather difficult.

Sex Tetris is one of the earlier examples of the lively Spectrum scene that evolved after the collapse of the Soviet Union on its former territory. There is another, later, game of the same name, that to avoid confusion is usually listed as Sex Tetris 2.