For all the aspiring young actors and actresses out there, the most important takeaway from the above interview with "The Mortal InstrumentsCity of Bones" co-star Jared Harris is that "acting's fun."

Harris sounds like he indeed had quite a bit of fun performing alongside Lily Collins and the other young star on the film's elaborate sets. 

In the movie, typical teenager Clary Fray (Collins) discovers her true identity as a shadowhunter, a half-human/half-angel warrior who fights the forces of darkness who are unseen but normal humans. It's based on a series of bestsellers by Cassandra Clare. Harris, who plays Hodge Starkweather, tutor for the Shadowhunters.  

HitFix recently sat down with co-star the "Mad Men" star, who also played the villainous Moriarty in "Sherlock Holmes: A Game of Shadows." He discusses familiarizing himself with the books' dense mythology, in a way that reflected Hodge's own overarching knowledge of the Shadowhunters' legacy.

Harris also touches on working with director Harald Zwart ("The Karate Kid" remake), the film's divergence from "Harry Potter"-style magic, acting alongside with youngsters, "The Dumbledore Connection," and -- of course -- his time on "Mad Men."

"The Mortal Instruments: City of Bones" also stars Jamie Campbell Bower, Kevin Zegers, Jemima West, Godfrey Gao, Lena Headey, Jonathan Rhys Meyers, and Kevin Durand.

"The Mortal Instruments: City of Bones" opens August 21.