The estate of Johnny Cash should be more upset that his likeness could be made to sing ‘Smells Like Teen Spirit’.
Why?
Johnny covered fellow grunge act Soundgarden’s Rusty Cage on Unchained.
And that is just one of the many 90’s era songs he covered on The American Recordings albums.
I agree that Smells Like Teen Spirit wouldn’t be the most interesting one for Johnny to cover, if he were still alive of course. Personally, I can almost hear him covering Come As You Are.