“He's as mad as a hippo with a hernia.”
“And the Hippos were boiled in their tanks!”
“The drinking of coffee is an absolute sin! Our Glorious Prophet did not partake of coffee because he knew it dulled the intellect, caused ulcers, hernia and sterility; he understood that coffee was nothing but the Devil's ruse.”
“...about as noticeable as a hippo in a flower garden.”
“The hippo of recollection stirred in the muddy waters of the mind.”
“We traveled for two weeks with a pickled hippo.”