Upon graduation from Phillips in 1976, he entered Harvard College. From his freshman year onward he received important roles in campus stage productions. When Clemenson starred in a Harvard Lampoon sketch comedy show, a Harvard Crimson theatre critic described Clemenson as "hugely talented actor who can trigger hysteria with any of a dozen subtle expressions or inflections." Other Crimson critics described his performances in Shakespeare plays as "a tour de force of sheer talent and intelligence" (in "The Winter's Tale") and "a very fine and subtle performance" (in "Measure for Measure"). He displayed early on his remarkable range when he undertook with inimitable flair and hilarious effect the hugely solemn role of Erde "the green-faced torso", goddess of the Earth, in Peter Sellers's Loeb Drama Center production of "Wagner's Ring" (1979).