Sumomo is a bit character in Sgt Frog Abridged. She is a famous intergalactic singer with a smooth, feminine singing voice and a deep, raspy speaking voice. Keroro attempted to use a talking doll of her to gain viewers for the platoon's radio show in Episode 6. Her second and last appearance is singing in Episode 8, presumably for the cartoon's theme song.
There are hints in Episode 6 that she finds Giroro to be cute.