The Rattlesnake's companion is the A-B-Sea Serpent, a large snake made up of a series of alphabet blocks, who teaches the Mer children their letters. The pair quarrel, but they're generally cheerful and are fond of riddles.
Once a year, the A-B-Sea Serpent and the Rattlesnake take a vacation. The pair surfaced in the Munchkin River, and met the Scarecrow, who was on a journey through Munchkin Country. They made friends with the Scarecrow, who found them charming and unusual. He invited them to visit the Emerald City, where they met Ozma, Betsy Bobbin, the Patchwork Girl and the Tin Woodman. (The Royal Book of Oz)