Nirvana requires no introduction. The trio left its mark rock history with Nevermind and have influenced countless other musicians in the two decades since the classic release. Anytime someone covers such a legendary group's music, you should be prepared to be criticized to the fullest. That is exactly what our friends at Pigeons and Planes have done. Covers including Lana Del Rey and the Muppets have been disected and either praised or ridiculed for tainting the melodies of Kurt Cobain and company.