© Fox
An upcoming episode will see Booth and Brennan travel to Key West, Florida, where they will encounter Walter Sherman, a military policeman known as 'The Locator'.
Nathan told Entertainment Weekly: "There have been a lot of terrific actors who have come in [for Walter, but] with a character like this, you just have to find the perfect fit. So even if someone is a brilliant actor... it might not quite work."
He added that finding the right actor to portray the "unique" character of Walter was a complicated process.
"You want to find people you want to see every single week [play] one... character," he explained. "And that is a rare, rare quality to find."
The Green Mile star Michael Clarke Duncan was recently cast as Sherman's partner Leo.
The Bones episode introducing Sherman is expected to begin filming next month.
