While the upcoming Manchester derby between United and City is being billed as the most important ever, the 131-year-old rivalry between the clubs has seen plenty of memorable matchups in the past as well.
Manchester City hosts its crosstown rival on Monday with the Premier League title possibly at stake, as United holds a three-point lead with three rounds remaining.
''This is the biggest ever derby,'' former United great Paddy Crerand told The Associated Press. ''The rivalry is extremely fierce and it's fiercer now than it has been for a very long time.''
Crerand should know.
He played in midfield when United lost out to City the last time the teams vied for the title in 1968 and took part in several of the previous big derbies. And with a rivalry stretching back to 1881, there's been plenty of those.
The club's first played each other back when United was a railway works team called Newton Heath and City was a church-based side called St. Mark's. Newton Heath won that first encounter 3-0, playing in the green and gold colors that current supporters wear as a protest against United's American owners, the Glazer family.
The teams first played each other as Manchester United and Manchester City in 1902 in the second division of the football league in a match that finished 1-1.
City won an FA Cup semifinal 3-0 against United in 1926, but it was not until the 1960's that the derby developed into the fierce rivalry seen today.
Like this year, the 1967-68 season saw both City and United vying for the league title. City boasted great players such as Mike Summerbee and Colin Bell in a strong team under the management duo of Joe Mercer and Malcolm Allison, while United could call on the famous trio of George Best, Bobby Charlton and Denis Law.
Although United won the first meeting between the sides, it was City that claimed a crucial 3-1 win at Old Trafford in March 1968 and went on to win only its second league title - and last to date.
''They were fierce matches back then, because United had a terrific side and City were very good as well,'' said Crerand, whose tough tackling backed up the attacking talent of Best, Law and Charlton.
''Derbies back then were different because you went out into the town at night - if you lost, you wouldn't go out,'' said Crerand. ''The players were friendly with each other - George Best was best man at Mike Summerbee's wedding, I think.''
Crerand said the 1968 encounter can't bear comparison to Monday's match because there was still a long way to go in the title race back then.
''In '68, we lost the derby but there were more games left to play,'' he said. ''We lost our last three home games, which would be unthinkable now.''
Law, United's second highest goalscorer, is also a lasting symbol of the derby rivalry. Starting his career with City, Law moved to United via Italian club Torino. The Scottish striker hit 237 goals in 404 appearances for United before returning to City as a veteran in 1973.
Struggling to replace an aging team, United was threatened with relegation in 1974 when City arrived for the derby with the end of the season approaching.
With the game petering out to a draw, Law was handed an opportunity to score with his back to goal and produced a brilliant backheel to give City the win.
Knowing the importance of the goal, Law refused to celebrate and walked off the pitch with his head bowed as the crowd invaded the pitch and forced the game to be abandoned. The result stood and United was relegated. Law subsequently retired and never kicked a ball again in league football.
''It was no more than a reflex action,'' he said later about the goal. ''And I felt sick. I have never felt so depressed in my life as I did that weekend.''
City's glee at the expense of its crosstown rival would not last.
United bounced back to the top flight at the first attempt and City would soon begin the slide that left the club languishing in the third tier by the end of the 1990s.
There were bright spots for City fans, however. In 1989, City inflicted a 5-1 home win on United, which had appointed an up-and-coming young Scottish manager called Alex Ferguson as manager three years earlier.
Ferguson went straight to bed when he returned home after the match.
''When my wife came in and asked what had happened I could hardly answer,'' he wrote later. ''I was in total shock and completely gone.''
City finally returned to the Premier League in 2002, gradually establishing itself in the top division without seriously challenging for trophies.
That all changed in 2008 when wealthy Abu Dhabi royalty took over City and began the spending spree of more than $1 billion on star players to reinvigorate the club.
The derby may have taken a while to warm up, but the return of City as a force in English football meant hostilities soon flared.
When Carlos Tevez defected to City from United in 2009, City erected a billboard with the Argentine's image and the slogan ''Welcome to Manchester'' - a sly dig at the poaching of a top player and the location of United's Old Trafford stadium which is just outside the city limits.
Ferguson reacted by branding City as ''noisy neighbors'' with a ''small club mentality'', but City's newfound wealth meant clashes between the crosstown rivals for silverware became more frequent.
Later that season, Michael Owen's stoppage-time goal earned United a 4-3 win at Old Trafford and United also won a two-legged League Cup semifinal against City.
Wayne Rooney's bicycle kick gave United a 1-0 win against City early the following season, but City's revenge came in the FA Cup semifinals, with a 1-0 win paving the way for the club to win its first trophy since 1976.
City manager Roberto Mancini was handed further millions to strengthen for a league title challenge this season and the investment paid off when Mario Balotelli scored twice in a thumping 6-1 win at Old Trafford last October to take a five-point lead of the standings.
''It's the worst result in my history, ever,'' Ferguson said. ''I can't believe the scoreline.''
As in 1989, Ferguson and United recovered quickly. But recent slip-ups in losing at Wigan and drawing with Everton have let City back into the race.
''The atmosphere in Manchester at the moment is electric,'' said Crerand, who now works for United's television channel MUTV. ''It's back at that top level where the two teams are fighting for the championship. I think it's great for the city.''
