The two clubs have had a monumental crossover down the years and no fewer than 69 men have represented both the red and blue sides of the city, according to the English National Football Archive.
It’s hardly surprising perhaps, given the comparative size of the two clubs – see how we kept things neutral there?
Here’s a run-through of a few players that you might have forgotten once called both Hillsborough and Bramall Lane home.
1. There have been more than you might think..
..and some made more of an impact across one or both sides of the city than others. How many of these had you sieved-out of your memory - wilfully or otherwise?! Photo: .
2. Jon-Paul McGovern
Surely more fondly remembered on the blue side of Sheffield, Scotsman McGovern scored at both the semi-final and final stages of the 2005 League One play-off success and became a fan favourite for his tireless running and fast feet, scoring eight league goals in 56 league outings between 2004 and 2006. Before that, though, the then-Celtic youngster spent a brief loan stint at Bramall Lane, where he had less success, making only 15 appearances. Photo: .
3. Paul Heald
A Yorkshire-born goalkeeper who started out his career with United before leaving in 1988 to enjoy success with Leyton Orient, Heald is perhaps more famous for being the Wimbledon keeper who couldn't keep out Tony Yeboah's thunderstrike in September 1995 than he is for either of his stints in Sheffield, where he returned in 2002 in the form of a loan stint at Hillsborough. Photo: .
4. Nathaniel Mendez-Laing
Not an overwhelmingly popular figure on either side of the Steel City, Mendez-Laing spent the better part of last season with the Owls before leaving on a free transfer in the summer. Some 11 years earlier he had spent a brief time on loan with United from Wolves, making eight appearances and scoring once. Both short spells were punctured by injury. Photo: .