Dons see off confident Celtic.
Dons manager Steve Paterson had confessed minutes before kick-off that all he had been hoping for was a defeat that was not too painful.
After all, his injury-ravaged side featured nine players under 21.
But when substitute Bryan Prunty, the former Celtic reserve, cancelled out Henrik Larsson's 15th-minute opener the stage was set for an upset no-one had been predicting.
The Dons rode their luck and won it at the death with a fine break that saw Australia international David Zdrilic slot past David Marshall.
It was the first time Celtic had been beaten in front of their own fans in the 77 games - since - Ajax had won a Champions League qualifier in August 2001.
With the title wrapped up with Sunday's win at Kilmarnock, there was hardly a competitive edge to the game.
And the news that Lisbon Lion Ronnie Simpson, the goalkeeper, had died meant there was no carnival atmosphere.
Celtic attacked regularly against nervous opponents and so jittery were the Dons that Larsson's 15th-minute goal had seemed a long time coming.
Momo Sylla set it up with a flick high over the Dons' defence and the Swede had no difficulty slotting past David Preece.
After the break, Celtic were content to meander along until Prunty shocked with a 56th-minute equaliser.
Muirhead was the man who made it happen with a low ball in from the left.
But the Dons were to have the final say and, after Muirhead had passed up a great chance in the final minute by blasting over, Zdrilic showed him how it was done by getting the better of Paul Lambert in a race for a long ball and slotting past Marshall.