Boogie Nights (1997)
The Unlikely Leading Man: Mark Wahlberg, a hitherto mostly untested rapper-turned-actor whose previous movie credits included a small role in The Basketball Diaries and schlocky thriller Fear .
How He Got The Part: When Leonardo DiCaprio turned down the role of porn star Dirk Diggler, he instead suggested his Basketball Diaries co-star Wahlberg for the role.
It was lucky that he did, because Wahlberg ended up with the first big dramatic role of his career, shushing naysayers with a performance that showed he was more than a pair of Calvin Kleins. And then he went and conquered comedy…
The Pianist (2002)
The Unlikely Leading Man: Adrien Brody, who beat out 1,400 other actors for the role of Wadysaw Szpilman, a musician caught up in the midst of World War II.
How He Got The Part: Director Roman Polanski thought he was the perfect fit for the role, and he wasn't wrong.
Brody lost weight, plus sold his car and apartment in order to get into character, proving he wasn't above a little extreme behaviour for his craft.
Super (2010)
The Unlikely Leading Man : The Office star Rainn Wilson, who here plays Frank, a regular guy who decides to become superhero The Crimson Bolt.
Think a middle-aged Kick-Ass.
How He Got The Part: Director James Gunn wanted John C. Reilly for the role back in 2002 when he wrote the script, btu Reilly was considered too much of a small fish.
Cue Wilson getting a popularity boost thanks to The Office . He was sent the script, loved it and the rest is history.
Bridesmaids (2011)
The Unlikely Leading Man: Chris O'Dowd, who plays Officer Nathan Rhodes in Kristen Wiig's laugh-out-loud comedy.
Wiig is thirtysomething Annie, who doesn't understand why Rhodes likes her so much.
How He Got The Part: O'Dowd proved he could hold his own against Wiig during a lengthy test session in which he had to keep up with her insistent improv-ing.
According to O'Dowd that session "went really well", and the rest is history.
Going The Distance (2010)
The Unlikely Leading Man: Justin Long. In this jet-setting romantic comedy, he plays Garrett, who attempts to keep his relationship with Erin (Drew Barrymore) alive despite living in different cities.
How He Got The Part: Long is sort of geek chic, which works perfectly for this rom-com role.
Plus, geeky romantic leads are en vogue at the moment thanks to the likes of Joseph Gordon-Levitt and Ryan Gosling, meaning Long was a shoo-in.
Caddyshack (1980)
The Unlikely Leading Man: "I don't get no respect!" was Rodney Dangerfield's catchphrase, but he finally got it as nouveau riche douche Al in this raucous chuckler.
How He Got The Part: By the time Caddyshack came along, Dangerfield had successfully created a comic persona for himself, meaning he was perfect for the oddball comedy.
In fact, he was so good that his tiny part was greatly expanded thanks to his knack for improvisational comedy.
Spider-Man (2002)
The Unlikely Leading Man: Tobey Maguire, whose casting as Peter Parker/Spider-Man caused comic fans to rant and rave.
How He Got The Part: Maguire was able to pull off the geeky Peter Parker part of the character expertly, but it was only after he'd hit the gym and honed himself into a muscle-bound hero that Sony agreed he really could be their Spider-Man.
Superbad (2007)
The Unlikely Leading Man: Jonah Hill, who plays high school senior Seth, a hopelessly inept virgin who has a massive crush on his Home Economics partner Jules (Emma Stone).
His plan to win her heart? Get a fake ID, some booze and hit up Jules' party…
How He Got The Part: Hill's perfect for Seth, confident in his comic timing and great as a loveable loser.
It also helped that Hill had impressed producer Judd Apatow with supporting roles in The 40-Year-Old Virgin and Knocked Up.
Sideways (2004)
The Unlikely Leading Man: Paul Giamatti, who played minor roles in films like The Truman Show and Big Momma's House before landing the part of Miles in this, Alexander Payne's wine-glugging romantic drama.
How He Got The Part: Giamatti's perfect for what's a pretty unconventional rom-com as it is - if somebody more conventionally good looking played Miles, it just wouldn't work.
Audiences seemed to agree. Giamatti became a huge star and Sideways went down like a fine Californian wine.
Gone With The Wind (1939)
The Unlikely Leading Man: Clark Gable, who played supporting roles in Hollywood flicks for a time before hitting the big time.
That wasn't until after he'd been ritually humiliated for his unconventional looks. While auditioning for a role in Little Caesar , for example, exec Darryl F. Zanuck derided him, saying: "His ears are too big and he looks like an ape."
How He Got The Part: Despite his 'odd' looks, Gable struck gold working opposite Jean Harlow in Red Dust before making five more films with her, gradually changing Hollywood's concept of what a leading man should look like and opening the door for Gone With The Wind.
For the now-classic book adap, Gable was the producer's first and only choice…
