Goals from Nick Proschwitz and Paul McShane sent Hull City into the Premier League as the Tigers fought to a 2-2 draw with champion Cardiff on a tense and action-packed final day of the Championship season.
With just minutes to go in the game, the Tigers were heading up against the 10-man Bluebirds, yet an incredible finale with one red card, two penalties and a mini pitch-invasion left the door open for Watford's 10 men to claim promtion in Hull's place.
Hull had to wait for the Watford result from Vicarage Road as third-place Watford was tied 1-1 at home with Leeds in a game delayed by 16 minutes in the first half by an injury to goalkeeper Jonathan Bond.
Hull led 2-1 when referee Keith Stroud awarded a late penalty for Ben Nugent's push on David Myler, prompting Hull fans to run onto the pitch. But David Marshall saved Proschwitz's spot kick.
"I thought when they scored the penalty, it was all over," Hull defender Paul McShane said. "I thought we were in the playoffs. You couldn't have written the script better."
The draw meant a goal for Watford would have seen it promoted instead of Hull, but Watford poured everyone forward and Ross McCormack's injury-time lob gave Leeds a 2-1 win.
"I have been around the block but I don't think I have ever witnessed anything like that," said Hull manager Steve Bruce, who used to play for Manchester United. "It's put us through the ringer ... It's just totally ridiculous."
Hull was promoted to the top flight for just the second time in its 109-year history. The Tigers had trailed to a goal by substitute Fraizer Campbell four minutes after the break.
But Proschwitz, a half-time substitute, guided the ball home from a cross by Stephen Quinn with 57 minutes gone and three minutes later McShane got his foot to a Robbie Brady corner to steer the ball home from close range.
Cardiff was reduced to 10 men when Andrew Taylor elbowed Ahmed Elmohamady in the closing minutes.
As a result, Watford had to be content with the playoffs after a game which saw them lose Bond, who had replaced Manuel Almunia before kick-off, to a neck injury which required hospital treatment.
Bond, who had come in as a late replacement for first choice Almunia after he injured a hamstring in the warm-up, was hurt in an accidental collision with teammate Ikechi Anya.
The Watford defender was pushed in the back by Leeds player Dominic Poleon, who was booked by referee Graham Salisbury, and collided with Bond.
After a long delay, Bond was carried from the pitch on a stretcher and taken to Watford General Hospital, where he underwent treatment and X-rays.
After the 16-minute delay Poleon scored when a mix-up between debutant goalkeeper Jack Bonham and Joel Ekstrand saw the defender try to hook a bouncing ball clear.
The ball hit Poleon in the chest and flew past the out-rushing Bonham to present Poleon with a simple tap-in.
But Anya made up for injuring his role in the keeper's injury when he cut in from the right and fed Almen Abdi on the edge of the area and he fired into the top corner to make it 1-1.
On the hour, Watford's Troy Deeney was shown a red for a second yellow card for a foul on Michael Brown.
McCormack then won it for Leeds, netting an injury time goal for when Bonham could only push his chip up into the air and the ball rolled over the line.
At the other end of the table, Peterborough was relegated after losing 3-2 at Crystal Palace and Wolves also went down following a 2-0 defeat at Brighton. Peterborough had led twice through Lee Tomlin and Nathaniel Mendez-Laing but their efforts were to prove in vain.
Barnsley led twice at Huddersfield and despite being pegged back did enough to stay up with a 2-2 draw.
Palace secured fifth place and a playoffs berth with goals from Glenn Murray, Kevin Phillips and Mile Jedinak, while Leicester sneaked into the playoffs with a 3-2 win at Nottingham Forest with goals from Matty James, Andy King and Anthony Knockaert.
Information from Press Association was used in this report.