Game of Thrones is finally back. After captivating audiences last year, the fantasy drama returns to HBO in the US on April 1 and airs just a day later on Sky Atlantic in the UK.

Of course, part of what makes the show so good is its top-flight cast, but what were they all up to before they fought for the Iron Crown? This week's Friday Fiver looks back at some of the Game of Thrones cast's greatest TV hits from years gone by!

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Lena Headey - Terminator: The Sarah Connor Chronicles
Before she breathed life into George R R Martin's morally bankrupt Cersei Lannister, English actress Headey was charged with bringing another iconic character to the small screen - Fox approached her to step into Linda Hamilton's shoes as robot-bashing action heroine Sarah Connor.

Headey starred alongside Thomas Dekker and Summer Glau in the show, which ran from January 2008 to April 2009. Unlike her current smash hit, Terminator: TSCC failed to pull in big audiences and got the chop, forcing the show's producers to abandon plans for a third season. Still, there's no denying the strength of Headey's central performance.

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Aidan Gillen - The Wire
Game of Thrones fans know Irish star Gillen as the scheming Littlefinger. But before he dealt in the political machinations of the Seven Kingdoms, Gillen was steeped in politics of a different kind on HBO's The Wire. From the show's third season on, he played Tommy Carcetti, an ambitious Baltimore politician who rose from the city council to the office of the Mayor of Baltimore.

Carcetti was a terrific character who breathed new life into The Wire - morally ambiguous, but charming and even sympathetic. Gillen nailed the US accent so effectively that many viewers didn't realise he truly hailed from the Emerald Isle.

Iain Glen - Downton Abbey
We were slightly torn here between old Jorah Mormont's role as Sir Richard Carlisle in Downton Abbey or his turn as Spooks villain Vaughn Edwards (the wrong'un that terrorised Lucas throughout series nine. Boo!)

But ultimately, we remembered that Downton is pretty much the biggest show in the world right now and it would be criminal to snub his appearance. Carlisle certainly rivals Vaughn in the bad guy stakes anyway, given that he blackmails Lady Mary (Michelle Dockery) emotionally and literally throughout their engagement. And with Mary ditching him for Matthew (Dan Stevens) in last year's Christmas special, perhaps his most devious schemes are still to come.

Jason Momoa - Stargate Atlantis
He may have had his hair restyled to play Khal Drogo, but most Game of Thrones fans should have no trouble recognising Jason Momoa as Stargate Atlantis's very own version of Chewbacca, Ronon Dex.

Although the Atlantis Expedition save Ronan from being hunted for sport by evil alien race the Wraith, his impressive physical capabilities and intimidating weaponry suggest they probably had a lucky escape. But as well as being able to convince as a badass, Momoa brought a certain human touch to this intergalactic role and managed to prove that he was more than just another hollow Baywatch body.

Sean Bean - Sharpe
Ned Stark may be gone, but the noble warrior lives on in our memory, thanks primarily to a charismatic performance from Sean Bean. Years before he played the Lord of Winterfell, Bean was a soldier of a different sort in the ITV drama Sharpe - based on Bernard Cornwell's popular series of novels.

The show's first run followed the gruff but heroic Richard Sharpe from Portugal 1809 to the Battle of Waterloo in 1815. Two specials, Sharpe's Challenge and Sharpe's Peril, aired in 2006 and 2008 respectively. Bean's made it known that he's keen to reprise the role once more, so only time will tell if we've truly seen the last of Sharpe...

Are you a Game of Thrones fan? Did you enjoy the stars' past work? Let us know below!