I've come across several free fonts here that derive from media that I recognize, such as the Breaking Bad font, TMNT font, and Mario fonts. I am hesitant to download any 100% free fonts and use them in my own commercial product because I fear they may be derived from media I'm not familiar with. So, how can I know if a font is original or not and can be safely used?

http://www.dafont.com/heart-breaking-bad.font
http://www.dafont.com/turtles.font
http://www.dafont.com/super-mario-256.font

Well, Turtles is mine, and I can way with 100 percent certain that I did that one from scratch based on the old TMNT cartoon.