When Timon and Pumbaa come looking for Mimipo, they overhear her crying and come rushing to her rescue. Once there, they try to comfort her by telling her that she can return to the Pride Lands - perhaps even receive a personal welcome from King Simba - but Mimipo cries that she's lost her sister, Sisipo. She then relates how she'd been swimming with her sister when the current had separated them, and now she's gotten herself lost in the jungle.
Seeing the young hippo's distress, Timon and Pumbaa vow to help her find her sister, much to the delight of Mimipo. Together, the three friends jump into the water and swim until they find Sisipo, who has a delightful reunion with her sister.
Sisipo is much larger than her sister, Mimipo, indicating that she may be the elder sister. She is broad and robust, with block-like features, a large head, and thick legs, and her hide is pinkish-gray. Her eyes are dark.