[1] Born and raised in Raytown, Missouri, Allen earned a Bachelor and master's degrees from the Boston University College of Fine Arts.
Earning rave reviews for his performance; he drew the attention of the producers of Rowan and Martin's Laugh-In and was invited to join the cast.
The series writers took full advantage of Allen's athletic abilities, and often cast him in blackouts as a hapless victim of circumstance who always gets knocked around.
Allen also created his own recurring character, "Chaplain Bud Homily", a mild-mannered parson who reflected on the spiritual things in life, only to be soaked with water, pelted with debris, or sent through trap doors in the floor.
When Rowan and Martin took charge of the Laugh-In series in 1972, they dismissed most of the cast members in favor of new faces, but retained those they considered most valuable: Dennis Allen, Ruth Buzzi, Richard Dawson, and Gary Owens; Lily Tomlin was kept on for limited appearances.