Nominated for the 1962 Tony Award Best Featured Actor in a Musical for his performance in From the Second City.
Was one of the original cast members of Second City in Chicago. Was responsible for shaping that theater's character in its early days.
Had three seasons with the American Shakespeare Festival in Stratford, Connecticut.
A founding member of Chicago's Compass Theater. Noted as a master of improvisational comedy, and, especially his pseudo-intellectual monologues. On screen, usually played eccentric roles. At his best as Soviet counter-intelligence agent Kropotkin in The President's Analyst (1967). Also played an evil doctor in two instalments of the 'Planet of the Apes' cycle ('Conquest of...' and 'Battle for...', respectively in 1972 and 1973).
Attended Mexico City College and the University of Chicago.
Along with Maurice Evans, he is one of only two actors to play a villain in more than one film in the "Planet of the Apes" series. He played Kolp in Conquest of the Planet of the Apes (1972) and Battle for the Planet of the Apes (1973) whereas Evans played Dr. Zaius in Planet of the Apes (1968) and Beneath the Planet of the Apes (1970).
His father Severn T. Darden Sr. was District Attorney of New Orleans.
Along with Charlton Heston, Roddy McDowall, Kim Hunter, Maurice Evans, Linda Harrison, Ricardo Montalban, John Randolph and Natalie Trundy, he is one of only nine actors to play the same character in more than one film in the original "Planet of the Apes" series. He played Kolp in both Conquest of the Planet of the Apes (1972) and Battle for the Planet of the Apes (1973).