The Scottish actor moved from Norse to Greek mythology to take on the role of sea deity Poseidon in Percy Jackson and the Lightning Thief, released on DVD and Blu-Ray earlier this month.
The 36-year-old is no stranger to characters of the historical and ancient world. Among his many other credits are Kingdom of Heaven, set in the 12th century; The Last Legion, set in the 5th century; and as Lucius Vorenus in the HBO/BBC series Rome, set in the 1st century BC.
He told us he hoped he had brought some of his "Scottish, Celtic fieriness" to the role of the gigantic Poseidon, who we first meet startling a fisherman as he emerges from the sea. It was a scene that wasn't as simple as it looked.
He explains: "The hardest thing for me, and it sounds like it should be a doddle, was the opening shot of me walking out of the water.
"I thought it would be dead easy and I'd be done by lunchtime but it took two days to nail that shot because being 40ft tall, if it just looked like I was walking down to the corner shop to get the paper it wouldn't work.
"When you're 40ft tall your bones are much bigger so there's much more dragging and momentum. I found that really tough, although I didn't think I would. I had to think about mime class at drama school and about how heavy my character was."
"Of course, it was great to be 40ft tall and to have the power of telepathy, to be able to communicate like Obi Wan Kenobi into Percy's mind."
The actor had been linked to the Thor role a couple of years ago. He confirmed at the time that his agent had been in talks with Marvel but said that the studio might want someone much younger. Subsequently, the studio issued a casting call for an actor in their mid to late 20s and then 26-year-old Chris Hemsworth - seen briefly as Kirk's doomed dad in Star Trek - landed the role.
In Percy Jackson, McKidd stars alongside several other Greek deities. We see Sean Bean as Zeus, CSI:NY actress Melina Kanakaredes as Athena and Steve Coogan as Hades.