Mr. Greenjeans, Captain Kangaroo's sidekick, who introduced a new animal each episode and taught children about caring for the earth was played by a man named Hugh Brannum. Hugh also played the characters Percy and Mr. Bainter the Painter on the show.
Before he was the lovable farmer on The Captain Kangaroo Show, Brannum was a jazz musician and a children's storyteller. He was born in rural Illinois in 1910 and moved with his family to California. He began playing music at an early age, playing brass instruments, the banjo and guitar, and his specialty, the upright bass. He played in bands during college, and during World War II played in a marine band led by Bob Crosby, Bing Crosby's brother. He eventually played with a band called Fred Warring and His Pennsylvanians who had a weekly radio show. The show also featured Brannum telling stories for children under the name "Uncle Lumpy" that focused on the adventures of a character named Little Orley. This segment of the show became quite popular and was released on records in the late 40s and early 50s.
In 1954 Brannum hosted a local TV show called "Uncle Lumpy's Cabin, and the following year joined with Bob Keeshan to form the Captain Kangaroo Show. After several decades, the show finally went off the air in the 1980s. Hugh Brannum died in 1987. His Uncle Lumpy recordings were re-released in the late 1990s, and Little Orley Stories and More Little Orley Stories released in 2000 by a children's toy company, Uncle Goose.
Oh, and reports that Frank Zappa was actually Hugh Brannum's son are entirely false. Apparently this story started because of a song on Zappa's album Hot Rats entitled Son of Mr. Green Genes.