Paul once said that they often had the tune first in their heads and often just used any old words while it was in progress, and for one, I can't remember which one, they just used the words on the label of a ketchup bottle (they were brainstorming around a breakfast table). Sometimes these temporary lyrics made it to the final recording session. I have often thought that the lyrics of pop songs can be a kind of auditory Rorschach where much or all of the 'meaning' is found in the listener's brain. See the phenomenon of the 'mondegreen' as well. Get Back
seems a fruitful source of these:
Jojo was a man who thought he was a woman/But he was another man.
Jojo was a man who thought he was a woman/But he was an ugly man
Jo Jo was a man who thought he was a loner/But he knew it couldn't last
One of my favourites is this miss - take on And I Love Her
- the misheard lyrics: She gives me everything, and tender veal; the real lyrics: She gives me everything, and tenderly. The contributor says: "It never crossed my mind that I might be wrong about these lyrics. I sang them, unexamined, for ca. 20 years before it dawned on me that my version was patently absurd. But hey, maybe tender veal is a British thing...who can say?"
This one is kind of revealing about the listener: "You've paid the tax, he's the queer of the shore" for "Newspaper taxis appear on the shore."