It is universally agreed that Paul and John brought out the best in each other and restrained each other's self-indulgences; but much as I loved John it was Paul who introduced me to the fact that songs could be clever as well as heartfelt, with smart lyrics, internal rhymes and the like. (Kern, Porter, Coward and Berlin were just names to me in those days.) He fuelled my incipient (since chronic) punaholism.
The earliest example I remember is the line "See how they run!" from "Lady Madonna", a record I can still picture as a 45rpm, though I suspect my mother threw it out decades ago. I got more or less right away - though at five I didn't know the term, then itself only 2 years old - that "See how they run!" was an intertextual reference to "Three blind mice". Later I learned that it was, more immediately, a quotation from Lennon's "I am the Walrus", though presumably with the same ultimate source - but in the context of "Lady Madonna" (unlike Lennon's maunderings) it took on real meaning, as a comment on the transience of human life and the inexorability of time.
It was probably a few years before I noticed the wordplay involved in its second iteration:
Thursday night your stockings needed mending -
See how they run!
It took a while for me to realise what was going on here because in my house stockings didn't run, they laddered. When I finally got the joke, perhaps at age 11, it was quite a revelation. The line didn't have just two meanings - it had three! I didn't know you could do that!
And that was how the pennies dropped from my eyes.