Mark was born to Russell, a Canadian diplomat, and Chloe, an architectural writer, McKinney. Since his dad was a diplomat Mark and his siblings spent most of their childhood traveling with him. Mark’s younger brother, Nick, is also a comedian and appeared on the short lived Comedy Central sketch comedy show The Vacant Lot. Mark attended a number of schools in cities around the world while traveling with his father, including Trinidad, Paris, and Washington D.C. He met Bruce McCulloch at the Loose Moose Theater Company, and the two joined with two other comedians to form the comedy troupe, ‘The Audience’, which performed at Theatresports. Later, Mark moved with Bruce to Toronto and met Dave Foley and Kevin McDonald. They combined to form The Kids In the Hall. He then later starred in the TV cult sensation, The Kids in the Hall (1988) . After the show was canceled in 1994, Mark became a cast member of Saturday Night Live (1975) from 1995 to 1997. Mark had roles in various movies including A Night at the Roxbury (1998), The Out-of-Towners (1999), The Ladies Man (2000) and Dog Park (1998) and Superstar (1999) which were both directed by Kids In The Hall co-star and friend Bruce McCulloch.