They are no longer hungry hungry hippos, they are now horny horny hippos.

Your hippos now have an eating disorder. Medical treatment costs twice your previous food bill

Granted. The goal of the game is now to eat the least amount of marbles. Nobody makes their hippos do anything and the game has turned into staring at unmoving plastic animals devoid of purpose. Somehow, its popularity outstrips all other sports and games. All televised sports are replaced with people staring at hippos. You find yourself in a tournament for charity. It never ends. You just stare at the hippos for what seems like eternity. What time is it? What day is it? How long has it been since the hippos hungered? Days? Weeks? Years?

Granted, your hippos are now half as hungry. You also now have twice as many hippos.

They were adopted by someone else, they are no longer your hippos

Granted.

They eat you.

Granted, marble population grows unhindered. You can’t walk down the street without slipping and falling on your arse.

Hippo Chow ain’t cheap.

Granted. They’re no longer hip.