Guess again! 
From the mid-50s:
Casey and Murphy were digging in a ditch;
Casey called Murphy a dirty son of a
Beaver, beaver, sittin’ on a log,
Along came a bumble bee and stung him on his
Cocktail, ginger ale, five cents a glass;
If you don’t like it, shove it up your
Ask me no questions, and I will tell no lies,
Casey hit Murphy, and now he’s paralyzed.
Correction on the above, line 3: Last word should be “rock.”
Not really a song, but:
I pledge allegiance to the flag,
Michael Jackson is a (slur).
Pepsi Cola burned him up,
Now he’s drinking 7 Up.
7 Up made him P,
Now he’s drinking Pepsi Free.
(For you kids, Pepsi Free was the forerunner to Diet Pepsi.)
7Up. The bottle with the big 7 on it and U. P. after. 
From south park:
Mrs. Landers was a health nut,
she cooked food in a wok,
Mr. Harris was her boyfriend,
and he had a great big
Cock-a-doodle-doodle,
the rooster just won’t quit,
And I don’t want my breakfast,
because it tastes like
Shih Tzus make good house pets,
they’re cuddly and sweet,
Monkeys aren’t good to have,
'cos they like to beat their
Meeting in the office,
a meeting in the hall,
The boss he wants to see you,
so you can suck his
Balzac was a writer,
he lived with Allen Funt,
Mrs. Roberts didn’t like him,
but that’s 'cos she’s a
Contaminated water,
can really make you sick,
Your bladder gets infected,
and blood comes out your
Dictate what I’m saying,
'cos it will bring you luck,
and if you all don’t like it,
I don’t give a flying fuck!