If the take away from Smell's like Nirvana is that being the subject of one of Weird Al's songs was a sign you had "made it" in the music industry — Amish Paradise shows that not everyone in the music industry was as awesome and Kurt Cobain.
Legally, Al does not have to seek artist's permission to record a song because they are parody. But because he is a nice guy, he always seeks permission. Coolio's lable signed off without asking Coolie. After the song was released and become a hit, Coolie said publicly that Amish Paradise was a "desecration."
Coolie is now a clown rapper.