The Manchester derby is one of English football's blockbuster fixtures, with Manchester United and Manchester City now two of the biggest clubs in the world.
Both clubs enjoyed success in the 1960s, but as Sir Alex Ferguson built United into a domestic and European force in the 1990s, City's fortunes waned.
The balance wasn't restored until 2008 when Sheikh Mansour completed his takeover at City and ploughed enormous investment into every part of the club. In the years since, the pendulum has swung the other way and it is City who have enjoyed great success.
Yet derby games remain as tasty as ever, when form goes out of the window.
Despite the rivalry, here's a look at the various players who have turned out for both clubs...
1. Billy Meredith
Welsh winger Billy Meredith was an early superstar of English football in the late 19th and early 20th century, playing over 700 games for City and United over a 30-year period between 1894 and 1924. That included a five-year hiatus when football was suspended for the First World War.
Meredith won the FA Cup with City in 1904 but was embroiled in a scandal the following year when he was accused of bribing an opponent. During his suspension, he was signed by United and debuted in 1907, winning the league in his first season and again in 1911, as well as the FA Cup.
He returned to City in 1921 at the age of 47 and played on for another three years.
2. Denis Law
Denis Law spent the 1960/61 season at Manchester City, before being tempted to Torino for a record transfer fee for a British player.
He returned to Manchester a year later, but to join United. Law went on to enjoy a stunning 11 years at Old Trafford, scoring 237 goals in 404 appearances (only Bobby Charlton and Wayne Rooney have more) and helping the club to their first league title since the Munich disaster.
He rejoined City in 1973, and famously scored a backheel on the final day of the season against United, who were later condemned to relegation, in what became an iconic British football moment.
3. Brian Kidd
Manchester born and bred, Brian Kidd progressed through the United academy and went on to score 52 times in 203 league appearances, as well as winning the European Cup in 1968.
Following the club's relegation in 1974, the forward moved to Arsenal, but was back in his native Manchester two years later, this time lining up in the blue of City. Kidd was prolific during his three years at Maine Road, scoring 44 times in 98 league appearances.
Alex Ferguson brought Kidd back to United in 1988 to coach the youth team, and he became Fergie's assistant in 1991. After various managerial and coaching spells elsewhere, Kidd switched Manchester allegiances once more, joining the City coaching staff in 2009.
4. Terry Cooke
Terry Cooke progressed through the youth ranks at United just behind the Class of '92, but competing with David Beckham for a place in the team limited the winger to just eight first-team appearances.
Cooke initially joined City on loan in Division Two in 1999, which was later made permanent for £1m, although he struggled to establish himself long-term once the club started rising back up through the leagues.
5. Peter Schmeichel
Peter Schmeichel spent eight years at United, playing his final game for the club club as captain in the 1999 Champions League final.
After spells at Sporting CP and Aston Villa, Schmeichel surprisingly moved to City for a season in 2002 and faced his former club.
Schmeichel was never actually on the losing side in a Manchester derby, whether playing for United or City.
6. Andrew Cole
Andrew Cole spent six hugely successful years at United after his £7m switch from Newcastle in 1995 - a then British transfer record.
He came into his own after Eric Cantona left the club in 1997 and later formed a lethal partnership with Dwight Yorke, with the pair scoring 53 goals between them in the 1998/99 treble season.
After spells at Blackburn and Fulham, Cole signed for City in 2005. He played one season with them but finished as the club's top scorer.
7. Carlos Tevez
Carlos Tevez spent two years on 'loan' at United between 2007 and 2009, winning the Champions League and successive Premier League titles as part of a stunning attack alongside Cristiano Ronaldo and Wayne Rooney.
However, in 2009 Tevez opted to switch allegiances and signed a bumper contract at City and making himself less than popular with the red half of Manchester.
His four seasons at City were a mixture of brilliant and bizarre. The Argentine scored goals straightaway, but later refused to come on as a substitute against Bayern Munich in 2011, disappeared home to play golf for four months, yet still returned later that same season to help City win their first league title in 44 years.
8. Owen Hargreaves
Owen Hargreaves saw his four years at United ravaged by injuries, but he was instrumental in the club's 2008 Champions League final win over Chelsea.
His Old Trafford contract expired in 2011 and the midfielder turned down the opportunity to play for Roy Hodgson's West Brom to sign for City. Despite scoring on his debut in the League Cup, he only featured once in the Premier League, before being released at the end of the season.
9. Abbie McManus
Abbie McManus is a member of an exclusive club of players who moved directly from one Manchester rival to the other. The defender grew up supporting United, but spent nine years at City across two spells.
She swapped red for blue in 2019 when United were promoted to the WSL but has already since moved on to Leicester.
10. Jane Ross
Jane Ross scored the goals that fired City to the WSL title in 2016. The Scot went on to win two more domestic trophies with the club, before moving on to join newly promoted West Ham in 2018.
One year later, Ross was back in Manchester. This time she was pulling on the red of United, although her time at the club proved fairly brief.
11. Aoife Mannion
Aoife Mannion made her name at Birmingham but was deemed good enough by City to join them in 2019. However, a long-term knee injury defined her time at the club and she was released in 2021.
Mannion found a new home at United, reuniting with ex-Birmingham manager Marc Skinner.