Nae exactly a sang parody, but sin ye mention MAD magazine, here's the stairt o ma favourite bit o theirs, whilk wis ca'd sumpit like "Legend o the Ad-men." (Forgie ony mispellings, as Ah'm daein this frae memory):

'Twas brillo, & the G.E. stoves
Did Procter Gamle in the Glade;
All Pillsbury were the Taystee loaves
And in a Minute Maid.

Beware the Ad-men, Oh, my son:
The voice that lulls, the ads that vex
Beware the .....(?) and shun
That horror call'd Brand X.

He took his Q-Tip swab in hand,
Long time the Tension Headache fought,
Then Dristan'd he by a Mercury
And .....? a while in thought...