Screen and stage actor Robert Morse has passed away. His agent confirmed the sad news to People magazine on April 21. He died after a "short illness," but no cause of death was given. Morse was 90.

Mad Men's Robert Morse has died

Born in 1931, Robert Morse enjoyed a highly acclaimed career on Broadway and in film and television. But he is probably most widely known from Mad Men, where he played "Bert Cooper," the eccentric co-founder of the show's Sterling Cooper agency.

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Morse's Mad Men role earned him five Emmy nominations, and he appeared until season 7. His character's death was followed by a memorable sequence in which "Don Draper" (Jon Hamm) envisioned "Cooper" performing a song-and-dance routine.

And Robert Morse is known for his award-winning stage work. He won Tony Awards for Tru and How to Succeed in Business Without Really Trying — the last of which also got a film adaptation in 1967.

Morse was also a talented singer and voice actor. Most recently, he'd been voicing "Santa Claus" on the animated series Teen Titans Go! He was also seen in The People v. O.J. Simpson in 2016.

Robert Morse would have turned 91 next month. He will be missed.