Moving beyond the forbidden crosstown football club line isn't something done all that often anymore, so it sticks out like a sore thumb when it does.
The Manchester derby is one of football's most storied rivalries and an integral part of the British game, especially in the wake of a resurgent Manchester City in modern times. More players than you'd imagine have actually crossed the fence, however, going as far back as 1890.
With Jadon Sancho signing for the Red Devils and becoming the latest to do so, here is everyone to have turned out for both United and City.
43. Bob Milarvie (Man Utd 1890/91, Man City 1891/96)
Having started in Scotland and moved down to England for more opportunities, Milarvie was already rather experienced by the time he joined Newton Heath in 1890.
He spent just a season with the club before moving to Ardwick, where Milarvie played as they switched names to Manchester City, before leaving in 1896.
42. William Douglas (Man City 1890/94, Man Utd 1894/96)
Douglas was a goalkeeper from Scotland who turned out for both Manchester sides as well as others.
After moving into England and wrapping up with Newton Heath in 1896, he played in Blackpool's first ever Football League game. Reports also suggest he went by the name Hugh.
41. Alf Edge (Man Utd 1891/92, Man City 1894)
A reliable forward who impressed with Stoke, Edge spent a year with Newton Heath before rejoining Stoke, having been suspended for playing for another club during that time.
He headed to Ardwick in his final year of football before retiring with Macclesfield.
40. Joe Cassidy (Man Utd 1893. 1895/00, Man City 1900/01)
Having headed to Manchester following a successful spell in Scotland, Cassidy scored the goal that kept Newton Heath in the First Division during his first spell.
After two years with Celtic, he rejoined Newton Heath and played for seven seasons, before briefly turning out for Manchester City.
39. Adam Carson (Man Utd 1892/93, Man City 1893/94)
Little is known about Carson's career, but the Scot moved down into England and played for both Manchester clubs after a spell with Glasgow Thistle.
He also represented Liverpool.
38. Billy Meredith (Man City 1894/06, 1921/24, Man Utd 1906/21)
Meredith is considered as one of football's earliest superstar players. The Welshman was a hit for club and country and captained City to their first ever FA Cup win in 1904.
He moved to United two years later and enjoyed an up and down spell that was interrupted by the war. He returned to City in 1921, and remains the oldest player to play for United aged 46.
37. Bert Read (Man City 1895/02, Man Utd 1902/08)
Born in Stretford and raised throughout Manchester, Read was a full back by trade.
After a successful time with City, Read moved to the renamed Manchester United in 1902 and stayed there for six years.
36. Frank Barrett (Man Utd 1896/00, Man City 1901/02)
Barrett was already a goalkeeper with international merit upon joining Newton Heath in 1896, having already been capped for Scotland.
He headed over to Merseyside upon his departure, but returned to Manchester in 1901 with City.
35. Stockport Smith (Man City 1897/00, Man Utd 1901/02)
Real name William, Stockport Smith was a wide player and a forward who started at Stockport County, before moving onto City and briefly United.
With City having two William Smiths on the books at the time, one was referred to as Stockport and the other Buxton to avoid confusion. Bring back nicknames by Mancunian borough.
34. Hugh Morgan (Man Utd 1900/01, Man City 1901/02)
The Scot had somewhat of a journeyman career before it was ever a thing.
Starting in his country, he moved to England to sign for Sunderland in 1896 before heading further down for Bolton and eventually the two Manchester sides. He wrapped things up back in Scotland.
33. Daniel Hurst (Man City 1901/02, Man Utd 1902/03)
After starting as an amateur and impressing with Blackburn, Hurst moved in and out of the Football League in a relatively short career.
An impressive one year spell with City was followed by a single season at United where again he looked good, but Hurst retired in 1903.
32. John Christie (Man Utd 1902/04, Man City 1904/07)
Starting in the Football League, Christie spent two years with United before switching to their neighbours.
His career would end up heading down south into the Southern League, before serving in the First World War in the Royal Air Force.
31. Jimmy Bannister (Man City 1902/06, Man Utd 1906/09)
Little is known about Bannister beyond his spells with the Manchester sides.
United purchased him from City after a successful few years, and he helped them win the league in 1908 before departing a year later.
30. Sandy Turnbull (Man City 1902/06, Man Utd 1906/15)
Scottish forward Turnbull moved across to United with Bannister in 1906 following malpractice at City.
He scored the only goal as United won the FA Cup final and last appeared for them in 1915, before serving in the war and being killed in the 1917 Battle of Arras.
29. Herbert Burgess (Man City 1903/06, Man Utd 1906/10)
The third to switch allegiances following City's punishment for malpractice, Burgess had a fascinating career at such a time.
After moving to United in 1906, he left to play in Denmark in 1908 while still on the books, before leaving officially in 1914 to play for Hungarian side MTK Budapest, and then enjoying a coaching career throughout Europe.
28. George Livingstone (Man City 1903/06, Man Utd 1909/15)
The Scotsman seriously got about during his playing career.
He played for Celtic and later Rangers in Scotland, and turned out for Liverpool as well as both Manchester clubs during his career. He remains the only player to play for both Manchester sides and the two Old Firm sides.
27. Horace Blew (Man City 1906, Man Utd 1906)
Despite making just two appearances in the Football League throughout his career, Blew was a regular in the Wales national team.
Blew's best stuff came in the Welsh football system, making just one appearance each for both United and City.
26. Herbert Broomfield (Man Utd 1907/08, 1910, Man City 1908/10)
The goalkeeper from Cheshire had two spells with the Red Devils either side of a two year stint with Manchester City.
Little else is known about his career.
25. Mickey Hamill (Man Utd 1910/14, Man City 1920/24)
An Irishman with an impressive journeyman career, Hamill initially started in Gaelic football.
United signed him after he impressed in a friendly in 1910, but he spent time back at Belfast Celtic and on loan in Scotland with Celtic during the war, before returning to Manchester with City in 1920.
24. Wilf Woodcock (Man Utd 1912/20, Man City 1920/22)
A seriously local lad, Woodcock was born in Droylsden and started with Abbey Hey and Stalybridge Celtic before making it at the Red Devils.
An eight year stint unfortunately fell throughout the First World War, and he joined City in 1920 for a brief period.
23. George Albinson (Man Utd 1920/21, Man City 1921/22)
Little is known about Albinson's career beyond his brief stints with either Manchester club.
Albinson was from Bury and made his United debut in a defeat to Liverpool.
22. Bill Dale (Man Utd 1925/31, Man City 1931/38)
Allegiance switching was beginning to calm down ever so slightly by this point as football grew in popularity between war times.
Dale joined United as an amateur in 1925 and went professional a year later, but only made 64 appearances in six years. He made 236 for City in an eight year spell, winning the Charity Shield in 1937, before the war broke out in 1939.
21. Harry Rowley (Man Utd 1928/32, 1934-37, Man City 1932/33)
The forward played for a number of clubs including Shrewsbury and Oldham in between his stints with the two Manchester sides.
Rowley is more commonly remembered for his exploits with the Red Devils.
20. Bill Ridding (Man City 1930/31, Man Utd 1931/34)
A prolific spell with Tranmere earned Ridding his move to City in 1931 for a £3,500 fee, but he only stuck around for a year before he was snapped up by their local rivals.
Ridding is best remembered for his managerial exploits, guiding Bolton Wanderers to the 1958 FA Cup.
19. Len Langford (Man City 1930/34, Man Utd 1934/37)
The English goalkeeper's brightest spell in Manchester was on the blue half, making over 100 appearances over four years.
He then moved to United, but played less frequently.
18. Denis Law (Man City 1960/61, 1973/74, Man Utd 1962/73)
A fact that many won't know. The man with a statue outside Old Trafford actually first played for their crosstown rivals.
City signed Law in 1960 for a then British record fee, but left for Italy with Torino a year later. He returned to Manchester with United and became an icon, winning two league titles, an FA Cup and the European Cup in Sir Matt Busby's rebuilt side.
17. Brian Kidd (Man Utd 1967/74, Man City 1976/79)
Coming up through the youth ranks at United, Kidd scored in the 1968 European Cup final on his 19th birthday.
He left for Arsenal as United declined and were relegated in the 70s, but returned to Manchester with City in 1976. After initially coaching at United, a rift with Sir Alex Ferguson led Kidd to City again, where he has spent the bulk of his coaching career.
16. Wyn Davies (Man City 1971/72, Man Utd 1972/73)
After putting in the reps with Bolton and Newcastle, Welshman Davies earned a move to Maine Road in 1971 and enjoyed one successful season there.
His next move wasn't far, being bought by Frank O'Farrell - the man replacing Busby at United. He was sold a year later, however, with O'Farrell sacked and United barely avoiding relegation from the First Division.
15. Sammy McIlroy (Man Utd 1969/82, Man City 1985/86)
Busby's final signing at United, McIlroy proved a loyal servant having moved over from Belfast.
The midfielder was a reliable hand over ten seasons for the Red Devils, winning the Second Division and the FA Cup before his 1982 transfer to Stoke. He joined City in 1985, but only stayed for one season.
14. Peter Barnes (Man City 1974/79, 1987/88, Man Utd 1984, 1985/87)
His goal in the 1976 FA Cup final for City earned Peter Barnes the PFA Young Player of the Year award for that season.
A tricky winger, Barnes played for just about everyone around spells at both Manchester clubs. Literally. Having been signed for United by Ron Atkinson, Barnes used to hide from Sir Alex Ferguson in order to avoid getting the hairdryer treatment. Who wouldn't?
13. John Gidman (Man Utd 1981/86, Man City 1986/88)
After winning the League Cup with Aston Villa, Atkinson made full back Gidman his first signing at United in 1981.
Gidman fared well at Old Trafford, helping the club to two FA Cup wins before being sold to City in 1986, where they were relegated to the Second Division.
12. Peter Beardsley (Man Utd 1982/83, Man City 1998)
For as good a footballer as Beardsley was, neither of his two stints in Manchester were all that memorable.
He made one appearance for United in the League Cup, and his loan spell at City was a short one. Still, it makes him the only player to have featured for both top-flight teams in Liverpool and Manchester.
11. Mark Robins (Man Utd 1986/92, Man City 1999)
A young Robins played a key role as Ferguson lifted his first trophy as United manager in 1990, scoring against Oldham in the semi-final replay.
A bright start at United fizzled out, but Robins enjoyed a fine career elsewhere and returned to Manchester briefly in 1999 with City in a loan spell, disrupted by injuries.
10. Shaun Goater (Man Utd 1988/89, Man City 1998/03)
Feed the goat and he will score. City's heroic striker actually started as a youth product at Manchester United, and despite signing professional terms, he didn't break through.
Goater burst to life at City as a prolific head who fired them up the divisions and stopped them slipping once more. His 100th goal for the club also came against United; fitting.
9. Andrei Kanchelskis (Man Utd 1991/95, Man City 2001)
The tricky right winger was electric for United in the early 90s and a key figure in the early years of the Premier League.
He fell out of favour following David Beckham's ascent and drifted from Ferguson, leading to his 1995 sale to Everton. His return to Manchester was a temporary one with City, being loaned from Rangers with little significance.
8. Peter Schmeichel (Man Utd 1991/99, Man City 2002/03)
Having left United a hero in 1999, bowing out as a treble winner, Schmeichel dampened his legacy when he returned to Manchester in 2002.
He retired after one season with City having never lost a Manchester derby, but famously got daggers from Gary Neville in the tunnel pre-game and fell out of favour with some United fans as a result of the move.
7. Terry Cooke (Man Utd 1991/94, Man City 1999/02)
Tipped for a bright future after excelling for United at youth level, Cooke couldn't make it stick in the first team and was loaned several times.
The last of those loans was to City in 1999, who brought him to Maine Road permanently as a result.
6. Andy Cole (Man Utd 1995/01, Man City 2005/06)
Considering just how good Cole was up top for United in the 1990s, a one season move to their rivals at the end of his career wasn't one that bothered fans all too much.
Probably more so because he was a bit knackered by that point, and considered less of a legend compared to Schmeichel.
5. Tony Coton (Man City 1990/96, Man Utd 1996)
After impressing and winning Player of the Year awards as City's goalkeeper in an up and down side, United swooped in and snatched Coton mid-season in 1996.
Coton served as understudy to Schmeichel and never really got a look in in a six month spell, but has since returned to the club as their goalkeeper scout.
4. Jon Macken (Man Utd 1995/97, Man City 2002/05)
Macken was another youth prospect that never broke through at United, but returned to Manchester with City in 2002 after impressing at Everton.
Macken never really kicked on having been regularly bogged down by injuries.
3. Carlos Tevez (Man Utd 2007/09, Man City 2009/13)
Famous for his financial antics with Kia Joorabchian, Tevez spent two years ripping up the Premier League and Europe with United.
But that infamous third-party ownership struck and City swooped, paying the big bucks United didn't have to fully own Tevez from 2009. United fans were outraged and gutted, while Tevez and City fans lapped it up. The Red Devils should've made that move permanent.
2. Owen Hargreaves (Man Utd 2007/11, Man City 2011/12)
Injuries blighted Hargreaves' entire career, but United were particularly gutted when it didn't work out for the tricky midfielder they'd snapped up in 2007.
Proving his fitness with some rather strange YouTube videos, City signed him on a free in 2011 for one season and he made four appearances. Possibly the weirdest transfer imaginable.
1. Jadon Sancho (Manchester City 2015/17, Manchester United 2021-)
Frustrated at a lack of first team opportunities, City lost grip on their exciting prodigy Sancho in 2017, who eventually moved to Borussia Dortmund despite interest from United.
Following a rather quiet, swift and uneventful saga - if only - United finally landed their man in 2021 for a £73m fee, bringing Sancho back to Manchester on the red side.