Jerry and Dorothy - Jerry Maguire (1996)
The original choice: The two leading roles in Cameron Crowes feelgood dramedy were actually written for two of the biggest A-listers at the time. Tom Hanks was in line to play Jerry Maguire and Winona Ryder was to be his supportive partner-in-crime Dorothy Boyd.
Who they went with: A perfectly-cast Tom Cruise - cmon, who else could have gone tet-a-tet with Cuba Gooding Jr.? - and fledgling star Renee Zellweger.
Douglas Quaid - Total Recall (1990)
The original choice: At one point during its turbulent, early pre-production stage Richard Dreyfuss was the hot pick to play the role of construction worker Douglas Quaid.
Who they went with: After Dino De Laurentiis dropped the option for the project, a quick-thinking Arnold Schwarzenegger approached the head of Carolco (who hed previously worked with on The Terminator) to buy the script and shoot it with him in the lead.
Gandalf - Lord Of The Rings/The Hobbit trilogies (2001-2014)
The original choice: Both New Line and writer-director Peter Jackson had their heart set on Sean Connery donning the wizard skivvies for the role of Gandalf. Despite offering the Scottish thesp a hefty portion of the box office takings, Connery turned it down due to not quite understanding the story.
Who they went with: The classically-trained Sir Ian McKellen. After transforming into two different iterations of Gandalf in the original trilogy, he reprised the role once more for The Hobbit series.
Princess Leia - Star Wars (1977)
The original choice: Its no secret that George Lucas and Brian De Palma held casting calls for Star Wars and Carrie at the same location. Luckily for the actors who attended this meant two chances to bag an important role. And for us? A chance to imagine Sissy Spacek as the gold bikini wearer, Princess Leia Organa.
Who they went with: Carrie Fisher, who, in a case of vice versa, also tested for the part of Carrie White in De Palmas thriller.
Clarice Starling - Silence Of The Lambs (1990)
The original choice: Three major names were circling the coveted role of FBI agent Clarice Starling before director Jonathan Demme settled on the final choice. Michelle Pfeiffer passed because of the dark subject matter and Laura Dern was an early favourite but was the studio believed she didnt pack enough of a punch.
The most unusual contender - who topped Demmes list - was rom-com star Meg Ryan, who outright refused when she read the script and dubbed it offensive.
Who they went with: After she rallied and championed Demme for a very lengthy period, he eventually gave her a chance and Jodie Foster snagged the role.
Han Solo - Star Wars (1977)
The original choice: The shortlist - which was actually pretty long - for the part of smart-mouthed Han Solo included a wealth of major names. After Al Pacino turned down the part, it came down to Kurt Russell (whose audition tape hints at a more understated take on Solo) and another completely unknown tradesman...
Who they went with:... which was of course, Harrison Ford.
Catwoman - Batman Returns (1992)
The original choice: Prior to the beginning of principal photography, Annette Bening was cast as the conniving Selina Kyle. When she fell pregnant shortly before the cameras were set to roll, Bening dropped out of the movie.
Who they went with: Right off the back of The Fabulous Baker Boys and Frankie and Johnny, Michelle Pfeiffer snagged the part and donned the lycra costume for Burtons superhero sequel.
Hagrid - Harry Potter (2001-2011)
The original choice: This could have changed the entire Potterverse had it come to pass. Warner Bros. originally made a deal with Robin Williams, who was eyeballing two different roles in the first Harry Potter, for him to appear as Hagrid.
Who they went with: When author J.K. Rowling exerted her influence over the adaptation she insisted on using an entirely British cast, which led to Robbie Coltrane bagging the part.
Forrest - Forrest Gump (1994)
The original choice: John Travolta was offered the part of Forrest Gump in Robert Zemeckis Oscar-winning biopic early on, and opted to pass in favour of a film by up-and-coming director Quentin Tarantino...
Who they went with: The dependable Tom Hanks who delivered the goods as the ambitious boy from Greenbow, Alabama.
Indiana Jones - Raiders of the Lost Ark (1981)
The original choice: The moustachioed Tom Selleck was officially cast in the role of archaeologist Indiana Jones and ready to begin the shoot, when an earlier pilot of his - Magnum P.I. - was picked up by the network. Contractual obligations meant Selleck had to pass on the adventurer.
Who they went with: Spielberg was keen to rope in one of the biggest hits from writer George Lucas Star Wars. Initially cool to the idea, Lucas came around and agreed that Harrison Ford was the perfect fit.