At least 3 games, Twins, Spider, and Hot Blocks, have the same maddening music playing which apparently was ripped from several Spanish Amstrad games, which makes sense because all 3 Mame games are by Spanish companies (Ecogames, Buena Vision, Nix). I wonder how many others there might be. Also, Spider was released as a DOS game, but the backgrounds were nudes, as opposed to the MAME version which has clean pictures of cars and stuff. However, only the shareware version of Spider seems to be available on archive.org, but the readme talks about a full version which you can pay for. This version seems to be lost, so I wonder if the arcade version was ever released with nude backgrounds also.