Curiously, Old Trafford's record attendance didn't even come in a United game. 76,962 supporters crammed into the stadium to see Grimsby take on Wolves in the 1939 FA Cup semi-final...
The Background: Just because United had exited the FA Cup in a third round replay - drubbed 5-1 at home by West Brom - didn't mean Old Trafford had seen its last knockout action of the season. Grimsby and Wolves met in M16 for the right to face the winner of Portsmouth and Huddersfield.
The Occasion: Already weakened by the absence of first-choice goalkeeper George Tweedy, Grimsby's plight worsened when his replacement, George Moulson, was injured early on. In the days before substitutes, the Mariners soldiered on with 10 men. Predictably, they were crushed. Wolves striker Dennis Westcott bagged four goals - en route to a season haul of 43 in as many games - while Tom Galley added a fifth.
The Aftermath: High-flying Wolves were crushed 4-1 by struggling Portsmouth in the final, with salt rubbed into the midlanders' wounds as Pompey held onto the trophy throughout World War II. OT's attendance record, meanwhile, cannot be beaten unless the capacity is further extended; it currently stands at 75,797.