Mark was born to a Canadian diplomat father, Russell, and an architectural writer mother, Chloe McKinney. His family's nomadic lifestyle, a result of his father's diplomatic career, led to Mark and his siblings spending a considerable amount of time traveling to various cities around the world. This unique upbringing enabled Mark to attend schools in several international locations, including Trinidad, Paris, and Washington, D.C.
Mark's younger brother, Nick, also pursued a career in comedy, appearing in the short-lived Comedy Central sketch-comedy show, The Vacant Lot. Mark's professional journey began when he met Bruce McCulloch at the Loose Moose Theater Company. The two comedians subsequently joined forces with two other talented individuals to form the comedy troupe, 'The Audience,' which performed at Theatresports.
Later, Mark and Bruce relocated to Toronto, where they crossed paths with Dave Foley and Kevin McDonald. The four comedians combined their talents to form the renowned comedy troupe, The Kids in the Hall. Mark's breakout role came with the TV cut sensation, The Kids in the Hall (1988),which unfortunately ceased production in 1994. Following this, Mark joined the esteemed cast of Saturday Night Live (1975) from 1995 to 1997.
Throughout his illustrious career, Mark has appeared in a diverse range of films, including A Night at the Roxbury (1998),The Out-of-Towners (1999),The Ladies Man (2000),and Dog Park (1998). He also starred in the films Superstar (1999) and others, both of which were directed by his close friend and Kids In The Hall co-star, Bruce McCulloch.