David William Thomas CM was born May 20, 1949, in St. Catharines, Ontario, Canada.
He is the eldest son of Moreen Duff (Muir), a Scottish-born church organist for thirty years, and composer of church music, and John Thomas(1926–1996), a Welsh-born medical ethicist, head of the Philosophy Department at McMaster University and the author of several books on philosophy and medical ethics.
His younger brother Ian is a Canadian singer-songwriter. The family moved to Durham, North Carolina where his father earned a Ph.D. in Philosophy at Duke University.
In 1973 Dave completed coursework for a Masters's degree in English Literature, majoring in Shakespeare, Chaucer, and Milton.
His first stage appearance was in the Toronto production of Godspell with Eugene Levy, Andrea Martin, Martin Short, and Paul Shaffer (music director).
He was a copywriter for McCann Erickson writing commercials for Coca-Cola in Toronto and New York (see below). Then Dave left advertising to join the Toronto cast of the comedy improv troupe, Second City.
An Emmy Award-winning TV show, SCTV, evolved from that stage show. This launched a 40-year career in film and television partially chronicled on this website.