Doogie Horner tells the History of the Beloved Children's Book Series The Berenstain Bears in McSweeney's.
Acording to Horner, the series was sold to to "Dalton Trumbo, who wrote the remainder of the series under the pseudonym "Dan and Jan Berenstain" (putting the man's name first—typical), sometimes collaborating with Mario Puzo, most notably on The Berenstain Bears Get the Gimmies."
(Link via Bookslut)