The one that used to get me was the opening line of Big Mouth Strikes Again by the Smiths
Sweetness, sweetness, I was only joking when I said I'd like to smash a greeters in your head
instead of every tooth in your head
So I just found out today that there is speculation that Yanis Varoufakis' wife is the subject of Pulp's Common People. In finding this out I also came across someone who thought the lyric was "She came from Greece she had a thirst for Norwich".
I remember my disappointment when I realised that the lyric in Creeque Alley about who is sat in the coffee shop is really (John) "Sebastian" rather than "the bastards".
Apart from the obvious Sue Lawley /So Lonely mondegreen The Police have another one.
In Message in a Bottle, I hear the lyric A year has passed since I broke my nose instead of the more obvious wrote my note