The role of Merlin proved difficult to cast, according to co-creator and executive producer Johnny Capps. "We had to find an actor who has a broad playing range, someone with the lightness of touch who will be able to deal with action and magic", Capps said in a 2011 interview. "We had an instinct about Colin. At first we weren't sure about him but then saw him again and again and we watched back his final auditions and said, 'He's perfect for the part.'" Before auditioning for the role, Morgan received the script for Prince Arthur by mistake. He only had five minutes before his audition to read over the correct part.
