â¢ Friedrich and Olejniczak, Evaluation of Carcinogenicity Studies of Medicinal Products for Human Use Authorised by the European Centralised Procedure (1995-2009) Regulatory Toxicology and Pharmacology, 2011 â(94/144) 65% cmpdstested positive, but only (11/94) 11% considered to hold human relevance 6
Talk0 Share. Clarabell the Clown was the mute partner of Howdy Doody. Three actors played Clarabell. The first was Bob Keeshan, who later became Captain Kangaroo. Keeshan was succeeded by Robert Nick Nicholson, who also played the character of J. Cornelius Cobb on The Howdy Doody Show.
Bob Keeshan. Robert James Bob Keeshan (June 27, 1927 â January 23, 2004) was an American television producer and actor. He created and played the title role in the children's television program Captain Kangaroo, which ran from 1955 to 1984, the longest-running nationally broadcast children's television program of its day. Keeshan also played the original Clarabell the Clown on the Howdy Doody television program.