Thanks to the Comic Book Resources for the following quotes. To read the full interview where the actor talks about a lot more about his work on the movie as well as some really interesting information about Kenneth Branagh, follow the link at the bottom of this page.
On Landing The Role Of Loki After Trying Out For Thor:
" I was told I was being tested for the role of Thor and I had half a day. So in mid-March last year, I came in and met with Craig Kyle and met Ken Branagh and did a test for Thor with Thor's blonde wig and facial hair and 20 pounds of extra muscle which I managed to find somewhere. And yeah, I think it was about a month later that I was back in London and Ken, Craig and Kevin called and said, "I just want to let you know that we have definitely and definitively found someone else for Thor, but we'd like to offer you the part of Loki." At which point I screamed and had to sit down on the pavement somewhere outside of a grizzly pub in North London and think about the rest of my life for a bit. Contemplate my existence. So that's how I got the part, yeah."
On The Loki We Will See And His Relationship With Thor:
"We're starting at the beginning, I think it's safe to say. I start in the film as Thor's younger brother, and I think in the manner of all younger brothers, I have a greater sense of freedom. I'm not the oldest, therefore the parental expectations aren't as heavy, so it's like a lot of younger children in sibling groups; I think Loki has a bit more freedom. He's not going to be King. He knows that. He has less responsibility on his shoulders so he's freer to have a bit more fun. Everybody at Marvel has been very clear and brilliant about coming into this that Loki just has...they're both enormously gifted. Thor and Loki are a two-man team and they're both going to run Asgard when Odin steps down."
"Loki's gifts are different in that he is sharper, he's cleverer, he's more interested in tactics and strategy. He's capable of thinking ahead and he enjoys chaos. So he enjoys reacting to chaos and that affects how he's the God of mischief. And so, I think that's where we start in that he's just physically not as strong, but he he's quicker and sharper, I guess that's fair to say. I think over the course of the story there are a couple of major shocks about Loki and his history and who he is. There are certain things that fans of the comics will already know, but hopefully you see Loki learn certain things about himself for the first time. So, it's a journey of self-awareness. As soon as he knows how powerful it is. that's when it becomes dangerous."
On The Difficulties Of Acting In Loki's Cumbersome Helmet:
"The horns are amazing! It was the last thing I got to try on when I did the costume fittings, and for me it was the most important thing. As soon as I got the part, I had nine months to prepare. I read all the comics. I read right the way through the history and I thought the horns are, well, it's like Spider-Man's suit. Loki isn't Loki without those horns on. Initially we were fitted, and it was a conversation of how much does it cover his face? How much does he use them as like a weapon, or is it just a statement of intent? It's kind of a representation of his soul in some way, like, back off because I'm dangerous. And it has been. We've had to work with it because they are very heavy. And because my ears are closed off, I can't hear very well and it becomes quite claustrophobic. It's a strange thing acting in it, but I know it looks so good because I've seen it in playback, so it's worth it."
On The Stunts And Fight Training Needed To Take On Thor:
"One of the first things I did when I came on board was start with stunt training. We thought it would be boring if Thor was a tank and it'd be boring if Loki was another tank and they were just running into each other. So we thought, if Thor is thunder and power and muscle and brawn, and he's got his hammer, Loki should be quick, like the wind. If Thor is heavy, Loki is light. We thought, what would be the weapon that Loki would be fighting with? So we thought throwing knives, because I think Loki doesn't like to get his hands dirty in a fight. He likes to be quick, efficient and lethal. It's like one blow - slam. I thought, if Loki could fight in a way that was as impressive as Thor's, but was completely different, so in a way, Loki is too quick and Thor can't catch him. I kind of conceived of Loki as a kind martial artist, almost a dancer. He dances his way out of combat. These knives are his way of keeping his foes at arm's length, but it's lethal. When you get one of those knives in, you're gone."
On Whether He Is Preparing To Play The Character Again In The Avengers:
"I may do, I may not. I know in the comics I do. I'm hoping I will. I genuinely know nothing. I haven't seen a script. Kevin mentioned it way back, but I think it's a long way off."