The producers took issue with Bruce Campbell shaving for the role. Bruce had insisted on it due to Sam's constant romancing of wealthy women, but the producers insisted he remain unshaved in order to provide contrast to Jeffrey Donovan's clean-cut leading man look. Consequently Bruce is only clean-shaven in his introductory scene.
When Michael (Jeffrey Donovan) is talking to David (portrayed by Mauricio Suarez) in his apartment about being bullied at school, he shows David his injuries from when he was attacked just after being notified that he'd been burned. He tells David that he holds 2 Black Belts and was still beaten. Jeffrey Donovan in actuality, is a martial artist having studied various styles for over 20 years, focusing on Brazilian Jujitsu for 6 of those years and holds a Black Belt in Karate.
The main theme song in the UK was different to the rest of the world when it was first shown on the "FX UK" channel. The music used for season 1 is "Men in Black 2" by Mottram and Johnson and can be found here on the www.audionetwork.com site.