The War of the Hippos was a long-lasting war from Hippo Story to Hippo Story 4 where George Aigaigy went up to Tyglo and called him a hippopotamus, causing the hippos to attack the Baby Army. It stopped when the War of the Shadows began at the end of Hippo Story 4.
Once, George Aigaigy snuck away from Sam's Kingdom and went to King Tyglo of the Hippos, telling him he was a hippopotamus. That angered Tyglo so much he sent Nupip Dolkose to steal Sam and bring him back to the Hippo Empire. Nupip obeyed, and easily snuck in and stole Sammy. However, Whalee rushed out and snatched Sammy back, then sending two Yippy Dogs after Nupip.