Somehow I passed over this the first time, but this time I googled...and discovered I had a filk convention songbook ("ConChords and Choruses", from the 1997 LA-area ConChord) that published the lyrics. So here they are in all their glory!

-- Gary
^^
Unified Field Theory
by: Jordin Kare
tune: "The Unicorn Song", Shel Silverstein

A long time ago back when physicists were green,
There were more kinds of theories than you've ever seen.
But there wasn't any one of them that always applied,
So the loveliest of theories would be unified.
   We had quantum mechanics; we had QED.
   Some special and some general relativity.
   Statistical mechanics we could point to with pride,
   But the loveliest of theories would be unified.

Now Einstein was a genius--of that there's no doubt.
There never was much physics that he couldn't figure out.
But there was just one problem that always taxed his brain.
And as the years went by, he was heard to complain:
   "I got my quantum mechanics, got my QED,
   My special and my general relativity.
   I've got a cat--but that's irrelevent. I've tried and I've tried,
   But my field theories just aren't unified."

Now, old Einstein passed on, and he came before the Lord,
And the Lord said, "Albert you deserve a reward.
Make any one request, and I'll be glad to yield."
He said, "Lord, I'd like the theory of the unified field.
   "I got my quantum mechanics, got my QED,
   My special and my general relativity.
   But I worked upon that problem 'till the day that I died,
   But my field theories just weren't unified."

Well, the lord said, "Albert, you're a very great man,
But not even you can fathom my vast eternal plan."
He pulled a sheaf of papers out of plain thin air,
And he handed them to Albert, and He said, "It's all there!"
   "You got your quantum mechanics, got your QED.
   Your special and your general relativity.
   Mass and time and energy and gravity tied
   Together in a theory that is unified."

Well, Einstein took those papers with a trembling hand.
He studied them in ecstasy, the theories were so grand.
Then he peered at one equation, looked back to page ten,
Sadly shook his head and sighed, "Wrong again!
   "I got my quantum mechanics, got my QED.
   My special and my general relativity.
   But as for field theories, in peace I'll abide,
   For the Lord Himself can't make one unified."

   So study quantum mechanics, study QED.
   Some special and some general relativity.
   But you might as well go hunting--just as sure as you're born--
   For a unified field theory--or a unicorn!