Day-Lewis, shortly before sunning himself on a passing iceberg to get into character.
"I was impressed by the depth of character achieved by the writers and wanted to be part of this amazing story," the actor reportedly said. "So I looked in the books to find an upcoming character that I could sink my teeth into. That's why I chose the role of Casso."
Casso, King of Seals, is a noble seal encountered on the streets of the Free City of Braavos. He is a seal.
"I immediately identified with the inherent nobility of Casso and his internal pain, which I thought I could embody effectively."
Casso is still a seal.
"We were, of course, delighted," said a clearly baffled David Benioff, executive producer on the show. "I mean, it's Day-Lewis, so of course we were on board. Then he said he wanted to play a seal and we were like, ....okay, I guess."
Day-Lewis is already doing his research for the role, spending hours researching the movement of seals and practising their surprisingly varied and subtle array of vocalisations.
"He insisted on auditioning," producer Dan Weiss confirmed. "He remained in character throughout, so the interview consisted of him coming in and barking at us in a seal-like fashion for an hour. Clearly, it was the greatest moment of my career, being barked at like a seal by Daniel Day-Lewis whilst he ate raw fish. For ages."
"I was excited to hear about the idea," novelist George R.R. Martin commented. "Especially as Casso has some major stuff coming up in The Winds of Winter." When pressed on the rumour that Casso may be the 'Pinniped That Was Promised', Martin chose not to comment.
Season 5 has not been formally confirmed yet, but HBO are likely to do so once Season 4 starts airing next week, unless they've decided they don't like money. And sweeping the Emmies next year with Day-Lewis's performance.