Ethel Rainicorn is the mother of Lady Rainicorn and the wife of Bob Rainicorn who appears in "Her Parents." She becomes quite excited upon meeting Jake for the first time. While Jake is impersonating a Rainicorn, she believes he is handsome and rich, and therefore a perfect match for her daughter. When she discovers that he is a dog, she becomes even more elated. She sympathizes with dogs as her husband Bob was saved by one during the Rainicorn-Dog Wars.
Ethel appears very supportive of Lady. As shown in a flashback in "Lady Rainicorn of the Crystal Dimension," Ethel and Bob were relatively unperturbed when Lady decided to flee to Ooo to hide the Crystal Mergence of Destruction, only showing concern that Lady might need groceries. Mostly, she and Bob were relieved that Lady was finally breaking up with Lee, whom they considered a "bozo." At the end of the episode, Ethel and Bob's grandson T.V. moves in with them.
She is a female Rainicorn with a long body, longer than Lady's. She has horizontal stripes with rainbow colors, a white horn, and light-blonde hair. She wears glasses with thick, round lenses due to poor vision. She also wears a universal translator device.
- She and Bob choose to wear the universal translator device (unlike their daughter).
- Ethel and Bob live on 47 Rainbow Street.
- Though speaking Korean, her mouth movements match what the translator is saying.