Sometimes on screen couples have chemistry that suggests they just have to get along famously even when the cameras aren't rolling. Other times, though, any on screen bonhomie is all fake.
Here are six famous couples who couldn't stand each other when the cameras stopped rolling!
Robert Downey Jr. & Terrence Howard - Iron Man
It might be hard to believe now, but reportedly Terrance Howard earned a higher salary than Robert Downey Jr for 2008's Iron Man. The film that launched Marvel's Cinematic Universe succeeded largely thanks to Downey Jr's wit and charisma, but Howard was - at the time - the more bankable star having previously received an Oscar nomination for Hustle and Flow. Howard had a multi-film contract to play Tony Stark's ally James "Rhodey" Rhodes, but didn't appear in the franchise again after the first one, being replaced by Don Cheadle for Iron Man 2 and 3.
Howard claimed that Downey Jr "pushed him out" of the Iron Man films in order to get a pay rise. He stated that he was offered "one-eighth" of what he was originally paid, in order to facilitate a huge rise in Downey Jr's wages. Having apparently helped his friend land the Iron Man gig in the first place, Howard reached out to his on-screen pal, only to find his attempts to reconnect totally ignored.
After this Terrence Howard left the franchise, and said he would not work with Downey Jr again. Meanwhile the Iron Man films - and MCU - continued on without him. Would the same be true had the money gone to Howard and the on screen embodiment of Tony Stark had left? I think we all know the answer to that.
Bette Davis & Joan Crawford - What Ever Happened to Baby Jane?
Hollywood legends Bette Davis and Joan Crawford played feuding actress sisters Blanche and "Baby" Jane in 1962's What Ever Happened To Baby Jane? and the behind the scenes shenanigans are even more legendary than the film itself. They had been in competition for decades before the film was made, but even with both on the down slopes of their careers, they weren't going out quietly.
In one scene where Jane (Davis) beats Blanche (Crawford), Crawford asked for a body double, fearful that Davis would actually harm her. For a close up, a body double couldn't be used, and Bette Davis used the opportunity to actually kick Crawford in the head.
In retaliation for that, Joan Crawford attached weights to her dress for a scene where Davis had to lift her out of bed. Robert Aldrich, the director, would be called by both women on a nightly basis to complain about the other!
Despite their well publicised differences, the two were due to work together again a couple of years later for Hush...Hush Sweet Charlotte, but Crawford pulled out a few days into filming. It was due to an illness, she claimed, but it's more than likely due to Davis' worse-than-ever on set behaviour.
Ryan Gosling & Rachel McAdams - The Notebook
Weepy romantic drama The Notebook is almost certainly your girlfriend's favourite film. The on screen love affair made stars of its leads, Ryan Gosling and Rachel McAdams, but for all their chemistry in front of the camera, off screen the two could not stand one another.
Director Nick Cassavetes revealed that during one scene, Gosling asked him to kick McAdams off set and replace her with someone else he could read lines with. The director did not do so, instead sending the two into a room together where "they started screaming and yelling at each other". Evidently getting it all out in the open worked, the atmosphere on set improved from there. Years later Gosling and McAdams actually ended up in a relationship in real life.
Tony Curtis & Marylin Monroe - Some Like It Hot
Some Like It Hot is Marylin Monroe's most famous and beloved star turn, but the blonde starlet was by all accounts a nightmare to work with on set. Co-star Tony Curtis hated her, a view shared by director Billy Wilder. Monroe's erratic behavior delayed production and added millions to the cost of the film.
Curtis said he would never work with her again after the film wrapped, and famously likened kissing Monroe to "kissing Hitler". However, in a book he wrote later in life, Curtis claimed the two had an affair during the filming of Some Like It Hot. If that's true it casts some doubt over his feelings for her during that time. What we do know for sure, though, is that the two didn't work together again after Some Like It Hot.
George Takei and William Shatner - Star Trek
The feud between Star Trek's Captain Kirk and Mr. Sulu is well known, and apparently still goes on even though the show has been off the air for decades.
George Takei has previously described "Bill" Shatner as "self-possessed" and "self-involved", while Shatner has labelled Takei "sick" and "psychotic". It all stems Takei's feeling that Shatner was not a team player during his Star Trek days, constantly trying to hog the camera and the limelight.
It's hard to imagine that Takei is the only co-star to have been annoyed by Shatner's massive ego, but he's certainly the most vocal about it.
Bill Murray & Lucy Liu - Charlie's Angels
Eyebrows were raised at the time when everyone's favourite hipster grandad Billy Murray agreed to slum it in the big screen version Charlie's Angels back in 2000. It was less surprising to see him fail to return for the sequel, and his non-appearance had a lot to do with a bust-up with Angels co-star Lucy Liu.
It's alleged that Murray incited the trouble, stopping mid-scene to address his co stars one by one, saying "I get why you're here," to Drew Barrymore, "and you've got talent," to Cameron Diaz, but then "what in the hell are you doing here? You can't act!" to Lucy Liu. Murray has since disputed this story, stating that the argument began over issues with the script. Whatever started the disagreement, something clearly kicked off, and I've never heard anyone deny the story that Liu attempted to physically attack Murray following his outburst.
Given that Liu has spent recent years doing voiceover work, TV movies and mediocre cop procedurals, maybe Murray wasn't far off the mark with his "you can't act!" comments.