-- Of German descent on his father's side.
-- Has one son, Hunter (born in November 2000), with partner Natalie
-- Hobbies include fishing, surfing, golf, and gardening.
-- Had a beret and coat to perform self-written Frank Spencer skits at the ages of 11 and 12 as school assembly entertainment.
-- His character of Cupid was originally written into the Xena: Warrior Princess season 5 finale episode "Motherhood" but Urban was unavailable because he was filming The Lord of the Rings elsewhere in New Zealand. As compensation, Rob Tapert wrote the season 6 episode "When Fates Collide" specifically for him, this time for his more popular character of Julius Caesar. Tapert also used this episode as am opportunity to bid farewell to two other fan favorite recurring characters; Alti and Brutus, portrayed by Claire Stansfield and David Franklin. "When Fates Collide" became one of the most popular episodes of the entire series.
-- Karl is, and has almost always been, very active. He worked on his aunt and uncle's farm for many years doing odd jobs. For filming the Lord of the Rings movies, he realized that Eomer was a consummate horseman and he was nowhere near that level, so he invested a lot of time learning-six to eight weeks, five days a week, two hours a day. He wanted to get to the point where he could neck reign-hold control of the animal with one hand while leaving the other hand free to wield a sword. He wanted to be so at one with the horse that he wasn't conscious or concerned about what the horse was doing. In addition, Karl also enjoys indoor rock climbing.
-- Was introduced in the second installment of the three big franchises he has appeared in: The Lord of the Rings: The Two Towers (2002), The Bourne Supremacy (2004) and The Chronicles of Riddick (2004).
-- Is good friends with his co-stars Viggo Mortensen from Lord of the Rings, and Renee O'Connor from Xena: Warrior Princess.