Regarding Cecil’s comments on Catnip, my cats, like Ivan, also go squirrely over olives. Not the olives themselves, those they ignore, but if I put the lid from the jar down for them, they roll all over it, rub their faces in it and try to fit themselves into it. Must be something in the olive oil…? 
I had a cat who was ordinarily very, very sweet and gentle, but he would attack for an olive. He would spear it on his claw. My theory was it was the salt.