In the 1500th and final match of his 26-and-a-half-year reign, the 71-year-old Scot watched the Baggies come from 5-2 down to seal an incredible draw at the Hawthorns
Sir Alex Ferguson brought the curtain down on his glorious 39-year managerial career in astonishing fashion as Manchester United drew 5-5 at West Brom in a match of incredible twists.
Goals from Shinji Kagawa and Alexander Buttner either side of a Jonas Olsson own goal put the champions three ahead with barely a third of the 1,500th and final game of their boss's United career played.
James Morrison and half-time substitute Romelu Lukaku reduced the deficit to a single goal with strikes either side of the break but Robin van Persie's 30th goal of the season and a Chicharito tap-in appeared to have handed United a comprehensive win.
But two more goals from Lukaku, whose hat-trick spanned just 40 minutes, either side of Youssouf Mulumbu's strike, in a five-minute spell late on gave West Brom a share of the spoils.
It marred the send-off for Ferguson, whose 26-and-a-half years in the United dugout ended shortly before 18.00BST when referee Michael Oliver blew the whistle on one of the most memorable Premier League matches of all.
Before the match, the Scot had been given a guard of honour by the two sets of players as he entered the pristine Hawthorns pitch on what was a glorious afternoon.
With both home and away fans rising to their feet to give the 71-year-old a standing ovation, he responded by lifting his arms above his head and waving to all parts, including his family in the Cyrille Regis suite.
One of the many Ferguson banners in the away end summed up the feelings of the United fans lucky enough to get tickets for this landmark fixture: "For 26 years, you gave us the world".
The manager was not the only giant of British football ending his top-flight career. Paul Scholes, in his 718th and final United game, had a 26-minute cameo that featured a series of tackles that verged on the reckless.
The Hawthorns was a haven for momento collectors, with the match programme, which featured a 38-page tribute to Ferguson, in especialy high demand.
For his final game, arguably the greatest British manager in history lived up to his pre-match pledge of selecting a forward-thinking team.
Stalwarts Ryan Giggs, Rio Ferdinand, Nemanja Vidic, Patrice Evra, Scholes, as well as David de Gea, all had to settle for places on the bench as Jonny Evans and Phil Jones formed a youthful centre-back pairing, left-back deputy Buttner made a rare start and Tom Cleverley, Kagawa and Anderson lined up in the midfield four.
One player who was not involved was Wayne Rooney, who is unlikely to have figured even if he had not been given permission to sit out the trip as wife Coleen was due to give birth to the couple's second child.
It took just five minutes for Ferguson's team to demonstrate how they wanted to give the manager the send-off that he would have craved. Chicharito's pinpoint cross from the right was met by the head of the unmarked Kagawa at the near post.
Three minutes later, United doubled their advantage as they once again used the full width of the pitch in a manner that has been a hallmark of Ferguson's Old Trafford tenure. Antonio Valencia, deputising at right-back, romped forward and his cross-cum shot was deflected into his own net by Olsson.
United's supporters responded by going through their full repertoire of songs, including the old favourite, "Let's all laugh at City".
In the 30th minute, the visitors went 3-0 up after Buttner seized upon a beautifully weighted pass from Cleverley and smited in a left-footed drive.
Just when it threatened to turn into a humiliation for West Brom, the home side mounted a fightback to place Ferguson's winning send-off in doubt.
Morrison nipped in from of Jones to pull one back for the Baggies five minutes before the break and, in the 50th minute, Lukaku's precise right-footed finish from the edge of the box gave his team hope.
Responding in the fashion that has been a signature of the Ferguson era, United swiftly added two more to give themselves a three-goal cushion.
Without discrediting West Brom's incredible fightback, the air of sentiment appeared to affect the visitors' decision-making. At 5-2, Chicharito, who normally only has eyes for the goal, opted to set up Scholes rather than rifle in a volley from close range.
With a ruthlessness that Ferguson would surely have admired, Lukaku and Mulumbu scored within 47 seconds of one another to set up a grandstand finish.
Ferdinand, the third of United's three pedigree subs, replaced Evans in defence but he could not prevent Lukaku sealing a famous comeback in the 86th minute with his third goal of the game and 17th league strike of the season.