It also helps that Mitchell, who resembles a scruffier version of Scandal's Tony Goldwyn, has been preparing for the role since he was 7.
"The first play I did was Hansel and Gretel at the Tarleton School," he says, referring to the Main Line pre-elementary academy in Berwyn. "I played Hansel and I loved it. When you're a kid and adults tell you you're good at something, you tend to keep doing it."
Mitchell, 44, also knows a thing or two about inherited bloodlines. He was born Silas Weir Mitchell Neilson at Lankenau Hospital and grew up a Flyers fanatic in the Paoli area.
He dropped the patronymic when he began pursuing acting as a career, both because it was cumbersome ("Four? Come on. Enough with the names," he says) and as a tribute to his great-great-uncle, now his namesake.
Silas Weir Mitchell (1829-1914) was a grandee in Philadelphia's Gilded Age, a renowned physician, poet, and author of novels usually set in Philadelphia, such as the historical Hugh Wynne, Free Quaker.
His groundbreaking work in neurology is cited as an influence on Sigmund Freud. And Mitchell, often credited as S. Weir Mitchell, discovered the medical phenomenon of the "phantom limb" based on his experiences as a surgeon in the Civil War. (Five of his novels were set during the War Between the States.)
At times, his scientific and imaginative interests collided, as when he wrote a short story, "The Case of George Dedlow," that created a sensation when it ran in the Atlantic Monthly in 1866. It was about a multiple amputee mystically restored, albeit briefly, by a spiritual medium.
"He got in a sort of War of the Worlds situation there," the actor says of his ancestor. "People thought it was real.
"There's an old photograph of him that my wife insists looks like me, but I don't really see it. He looks more like Donald Sutherland."
After graduating from boarding school in New Hampshire and Brown University in Rhode Island, the modern-day Mitchell spent a year in New York, "doing some terrible theater in basements."
He settled on the unusual course of studying drama at graduate-school level at the University of California at San Diego.
"I didn't think I was an actor with matinee looks who would get a lot of work in his early 20s," he says, "so you might as well take the time and hone your craft."
The result has been a long, busy run as one of TV's most distinguished character actors on shows like Silk Stalkings, 24, and Burn Notice.
Mitchell really made his mark with a pair of memorable recurring roles: Charlie "Haywire" Patoshik on Prison Break, and the wild-eyed Donny on My Name is Earl.
All that experience is evident in his performance on Grimm.
"Silas is a very smart actor, and he goes very deep into his character," says Jim Kouf, the show's other executive producer. "Whenever he questions a line of dialogue, it's very perceptive."
For Mitchell, it's all part of his ultimate goal: to transport viewers - even in a vehicle as outlandish as Grimm.
"I enjoy watching people who can create and inhabit a world so fully that you go with them. Like Claire Danes. Man, she is just amazing," he says.
"There's no formula for that. But you know it when you have it. I want my reality to be so real to me that you willingly forget your reality and come with me."
Lead on, Monroe. Just try to keep us out of the woods.
9 p.m. Fridays on NBC10