Birmingham City staged an astonishing great escape as they fought back to preserve their Championship status at Doncaster's expense, while Brighton also left it late to snatch the last play-off spot.
On a dramatic final day in the second tier, there were incredible scenes at Bolton's Reebok Stadium, where Birmingham looked dead and buried after falling 2-0 behind, only to snatch a stoppage-time equaliser to earn the 2-2 draw which lifted them out of the relegation zone on goal difference.
With 14 minutes remaining, second-half strikes from Bolton's Lee Chung-yong and Lukas Jutkiewicz had left Lee Clark's men on the verge of falling into the third tier for the first time in 20 years.
But the Blues were given a lifeline when Nikola Zigic headed home in the 78th minute and Paul Caddis then nodded in from close-range in the final moments to spark scenes of wild celebration from Clark and his players.
"It was unbelievable. I felt for my players, two down and staring down the barrel, because we were excellent all game, but they kept going. This is the biggest achievement of my career," said Clark, whose club is reportedly up for sale after former owner Carson Yeung was sentenced to six years in prison for money laundering.
"We have diced with death in sporting teams. I used the word 'Armageddon', because it's been difficult to attract players to the Championship, so if we went down and there was no fresh investment it would have been even tougher to attract the players to League One; that was my fear."
Doncaster had gone into the final round of matches one point and one place above the bottom three, but their 1-0 defeat at champions Leicester, sealed by David Nugent's 75th minute penalty, meant Paul Dickov's side will return to League One just 12 months after they secured promotion.
"Obviously we are gutted because it was everyone's aim to keep us in this division," Dickov said.
"We can look at our result today and results elsewhere, but more often than not you probably deserve to be where you are at the end of the season."
- Leapfrogged -
Millwall also had pre-match concerns about their safety, but Lions' boss Ian Holloway, who stared the season in charge of Crystal Palace, avoided falling two tiers in one year thanks to a 1-0 win over Bournemouth at The Den.
"It's the greatest achievement of my managerial career. We've got a proper Millwall team now," Holloway said.
There was an equally dramatic finale at the other end of the table as Brighton leapfrogged Reading into the end of season play-offs.
To make the top six the Seagulls needed a win at Nottingham Forest as well as a draw or loss for Reading against already-promoted Burnley.
Reading took the lead through a Kieran Trippier own goal, but Scott Arfield and Danny Ings put Burnley ahead.
Garath McCleary fired in a superb equaliser and that would have been enough for Nigel Adkins' side to reach the play-offs if Brighton hadn't staged a second half revival.
Forest had taken the lead in the 22nd minute through Matt Derbyshire, but Stephen Ward equalised in the 53rd minute before Leonardo Ulloa struck in stoppage-time.
"We knew that our players would never give up; that they would fight until the end and we got the goal we deserved. It is a special time to score," Brighton manager Oscar Garcia said.
Adkins added: "We can't change anything now. It's important you feel the pain and the hurt because that's what makes you work even harder."
That completed the line-up for the play-offs, with Brighton facing third placed Derby, who finished with a 1-1 draw at Leeds.
In the other tie fourth placed QPR, 3-2 winners at already-relegated Barnsley, take on fifth placed Wigan, who lost 4-3 at Blackburn.
Elsewhere, Yeovil finished bottom after losing 4-1 to Middlesbrough.