A bit of a tangent to Weird Al, who often is said to not need the permission of the original artist because his songs are parodies, usually isn't commenting on the actual content of the original song but instead takes the lyrics and gives them a different theme. 'Smells like Nirvana' is one of the few songs he does that actually does directly parody the original. His videos are far more parody than the songs themselves. Makes me wonder where the legal line actually is drawn and if asking permission is actually because it would be too risky not to.