Sometimes, the integrity of a good tune turns out to be more important (to the songwriter, anyway) than hearing the words clearly.
From 1961: Patsy Cline’s “I Fall to Pieces” sounds like “I Fall, Toopy Says”. I don’t know who Toopy is.
Moving to the 70s: ELO called their song “Strange Magic”, but the way the notes are accented turns it into a “Strange, Mad Jick” - again not sure what a Jick is.
Got any more? And, optionally, do you agree with the songwriter that a particular mangled lyric was worth it in return for maintaining the tune?