Considering their recent form, though, it is hardly a surprise. Now, when Sam Allardyce's men beat one of the big boys, there is less elation at an upset and more of a seriousness about this east London side that suggests they can do it every week.
Their work-rate certainly demonstrated that against Manuel Pellegrini's side - not that there wasn't jubilation after the game, anyway!
And there was one man who typified West Ham United's desire to beat City: Alex Song. Voted his side's man of the match, the former Arsenal midfielder was immense in midfield, fighting for every ball, registering an assist and making superb passes throughout the game.
At one stage, the 27-year-old ex-Barcelona man even took a cross with a rabona! Erik Lamela isn't the only player from London who can perform one of those...
Song's impact at the Boleyn Ground has certainly been felt and Gary Lineker has compared this West Ham side to the successful Hammers team of the 1980s - mainly thanks to Song.
Song is lifting West Ham to the dizzying heights of the 80's...and that's not just the length of his shorts.— Gary Lineker (@GaryLineker) October 25, 2014
And West Ham fans were just as pleased with the Cameroonian. Song has settled in effortlessly in east London and many onlookers are even suggesting the Gunners could do with him back.
Hammers supporters, though, were more focused on what he is currently bringing to his side. Here are their best reactions on Twitter!
How good was Alex Song? Arsenal could probably do with him. #WHUFC— Newstalk's Team 33 (@teamthirtythree) October 25, 2014