These come from Glitch - http://glitchthegame.com - an online game that shut down and donated all its assets to the public domain. The original files were .SWFs, unreadable to ordinary mortals, but Bart from opengameart.org converted them to an open format, SVG. The SVG files  were cleaned up and refactored by Anarres. Some have been changed a lot compared to the originals, so they are more like remixes than straight copies.