Actors Pedro Pascal and Michiel Huisman tell PEOPLE it was hard keeping their cool when they found out they'd been cast on the hit show.
"I used to watch the show like a regular fan," says Chilean-born Pascal, 39, who plays Oberyn Martell, a fierce and flirty prince who's in town for the royal wedding – he's lucky he missed the last one – and to settle a score.
Pascal, who previously had roles on The Good Wife and Homeland, says he was actually pretty bummed out after he auditioned for Thrones. "It didn't really seem like an attainable gig, so initially I was pretty upset about all the spoilers they'd given me during the audition!" he says.
Landing the major part "has really been really amazing," says Pascal, but that doesn't stop him from joking with the casting directors about his ruined fan experience.
"I told them, 'It's never going to be the same for me. I should have reconsidered the offer,' " he jokes.
Fans will be glad he didn't. "Oberyn lives dangerously and owns any room he steps into," Pascal says of his character. "And he's good in the sack."
Huisman's character, Daario Naharis, is the other smoldering swordsman joining the Game this season. The Dutch actor replaces actor Ed Skrein in the role of Daenerys's (Emilia Clarke) chiseled new soldier.
"I was in Amsterdam when they called to say I got the part," says Huisman, 32, who previously starred on Treme. To celebrate, "my wife and I had a glass of champagne."
For his scenes, Huisman filmed on location in Croatia. "Thank God I'm in the hot part," he says of the show that also films in wintry locales like Iceland. But being a leather-clad actor under the hot Croatian sun has its downside.
"By noon I was dying. In between takes I'd have someone on the crew throw ice cubes in the back of my costume, but I'd forget and when they'd melt a little it startled me. If you ever see me make a weird face on the show, now you know why."
His character, who only has eyes for Daenerys, brings the heat onscreen as well. "People keep asking me if it's a lot of pressure trying to romance the Mother of Dragons. But no. Emilia's amazing and funny. I couldn't be happier."
Season 4 of Game of Thrones premieres Sunday, April 6, on HBO.