Care Bears
Care Bears is an unreleased Atari 2600 game that Parker Brothers had in development in 1983, programmed by Laura Nikolich. It was meant to be a simple game for young children based on the popular Care Bears characters, but it was cancelled and never reached the shops. What survives is an early prototype that is closer to a graphics test than a finished game. You can try it here in your browser as a piece of Atari history.