The building that is supposed to be Michael's loft, is located on NW 7th Avenue, between NW 6th Street and NW 5th Street (528 NW 7th Avenue) Miami, Florida 33136. It can be found in Google Maps at 25.779033,-80.20706.
In the first season, Michael says he's had thirty years of karate training, but throughout the series, Michael also uses a variety of mixed martial arts including (but not limited to), Aikido, Brazilian Jiu Jitsu, and the Russian martial art Sambo. Michael says he has "combat experience on five continents" and "two black belts".
It's mentioned often throughout the series, that the name "Michael Westen" is notorious throughout Russia. Russian Intelligence talks about Michael Westen as having done too much damage to be one person (they think "Michael Westen" is a code name for a Special Operations team) and they use his name and tales of what he's done to scare rookie operatives.
The show uses the Coconut Grove Convention Center in Miami as production offices, and sets for Michael's (Jeffrey Donovan's) loft, and Madeline's (Sharon Gless') house. It had originally been slated for demolition.
During his fifteen-year tenure as a spy, Michael worked mainly in eastern Europe and the Middle East. As a result, he speaks fluent Russian and Farsi, and describes his command of the Polish language as rusty. He doesn't know Spanish, and is mocked repeatedly throughout the series for living in Miami without being able to converse in Spanish.
In the series finale, Fiona and Michael are in a cottage. That same cottage was in The Holiday (2006). It was the setting of Kate Winslet's house in England. Even the road leading to the cottage is the same.
Michael (Jeffrey Donovan) sustained a tooth injury during a lobster-eating contest in Nova Scotia at the time of casting. The Casting Director was taken with his solid jaw demeanor, and made Donovan talk through a clenched jaw to provide grit to the performance. Donovan was reluctant, however kept character throughout filming.
Through the series, when aerial shots of Michael's Dodge Charger, driving throughout Miami, are shown, a Miami Police cruiser can usually be seen a few car lengths behind, providing escort for filming purposes.
The gadgets "built" by Michael are fabricated by the Special Effects Department. It is a collaborative effort by the Writer, Production Designer, Special Effects, and the Prop Master. The actual builder is Michael Doyle, the Special Effects Foreman.
At one point, Jesse (Coby Bell) introduces himself as "Artest" and Fiona (Gabrielle Anwar) as "Shannon Brown". At the time, Ron Artest and Shannon Brown were the names of teammates on the Los Angeles Lakers.
Having a name with the same pronunciation, but different spelling as the character "Michael Westen", actor Michael Weston appeared in season three, episode five, "Signals and Codes", where he played "Spencer Watkowski".
Very early in her career, Sharon Gless (Madeline) played an undercover police officer on Emergency! (1972). Paramedic John Gage (Randolph Mantooth) took an interest in her. Once, she told Gage to lower his voice, or he was going to get her burned.
Sharon Gless (Madeline) and Tyne Daly were known for their roles in Cagney & Lacey (1981). Daly makes an appearance on this show as Tina, an asset Madeline cons into giving her information. She then becomes good friends with Tina, before having to burn her under Michael's order.