a highly-prolific character actor, most of his career has been in film and television, usually portraying a corrupt law enforcement officer. he had a recurring role on "cold squad" for four years, for which he won gemini awards in two consecutive years, and until the close of its ninth season had a recurring role on the science-fiction series "stargate sg-1". known for his perfect enunciation and his mellifluous deep voice, chalk is also a veteran of over 1,500 animated productions including "class of the titans", and the 2002 remake of "he-man and the masters of the universe". he is also known for his voice work in the "transformers" franchise as the voice of optimus primal in "" and "", and as optimus prime in the unicron trilogy. he also voiced the original megatron in an episode of "beast wars".