His most notable television appearances have come from recurring roles on Pure Genius, Private Practice, Prison Break, Grey's Anatomy, Scandal, and Agents of S.H.I.E.L.D..[1] His film credits include The Dog Lover (2015),[2] Ace Ventura, Jr.: Pet Detective (2009), Shuttle (2008), Sunshine State (2002) and Love Liza (2002).

Douglas's film appearances include Ace Ventura, Jr.: Pet Detective (2009), Shuttle (2008), Sunshine State (2002) and Love Liza (2002).

He also wrote and continues to perform across the country in the solo play Afraid to Look Down, which explores his journey in becoming a first-time father to son born with Down syndrome.

For the stage Cullen wrote and stars in the acclaimed and award-winning solo play Afraid to Look Down, which explores the journey he took in becoming a first-time father to a son born with Down syndrome.

Douglas received the "Lillie Stoates", a regional theater award, for Best Supporting Actor in a Play, for his work in The Orlando Theatre Project's "The Lion in Winter".