Substitute Will Buckley scored two late goals as newly-promoted Brighton started life at the Amex Stadium with a brilliant comeback win.
Doncaster looked set to spoil Brighton's big day after taking a first half lead through Billy Sharp.
The carnival atmosphere was dampened further when home boss Gus Poyet was sent to the stands.
But his decision to introduce Buckley proved a masterstroke as he grabbed the winner deep into stoppage time.
It was an emotional build-up to kick-off with the flag-waving home fans, many of who feared they would never see their side playing in a sparkling new stadium, creating a sea of blue and white in the stands.
But the game did not burst into life until the half hour mark after Kazenga LuaLua, a former Doncaster loanee, was denied a penalty after tumbling in the away area.
The midfielder was booked for his efforts - sparking a furious reaction from Poyet who was then ordered to sit in the stands by referee Eddie Ilderton.
Home striker Ashley Barnes could have cheered up the Uruguayan by converting a golden chance in the 36th minute but instead saw his placed shot scrambled off the line by George Friend.
Poyet's mood darkened moments later when much-coveted striker Sharp, who has stayed in South Yorkshire despite summer bids from Ipswich and Southampton, bagged the opener.
Brighton keeper Casper Ankergren managed to take the sting out of Sharp's effort before seeing the ball hit the inside of his post and trickle agonisingly over the goal line.
Worryingly for injury-ravaged Doncaster, Sharp was stretchered off following a robust challenge from Lewis Dunk after the restart and the departure of their talisman rocked the visitors.
A casual clearance from keeper Gary Woods nearly gifted Craig Mackail-Smith an equaliser before substitute Craig Noone screwed horribly wide with the goal at his mercy.
But it was another of Poyet's changes who stole the show as Brighton piled on the pressure.
Buckley, a summer signing from Watford, lashed home an 83rd minute leveller from the edge of the box after Doncaster failed to clear a Brighton free kick.
And the bulk of the 20,219 crowd went wild with ecstasy when, in the eighth minute of injury time, the 21-year-old forward calmly converted Noone's brilliant pass to seal a fairytale start for Brighton.