I thought they kind of sappily called the love letters they exchanged Strawberry Letters. Since he just received #22 from her this song he’s singing is #23 going back to her.
“Six Underground” by Sneaker Pimps, only once does the whole title appear. The rest of the time only “underground”.
“Fortunate Son” by Creedence Clearwater Revival has “_____ son” and “fortunate one” but not “fortunate son”.