Yep.

It's settled then. Mama Luigi is canon.

Let me answer your riddle with a riddle. A box without hinges, key, or lid, yet inside golden treasure is hid.

Exterminator here. Generally speaking, when poison expires, it becomes less poisonous. Keyword being less, so it's not exactly inert. It's still somewhat hazardous, it's just no longer able to be used properly.

Its color is the same as its name, just like a lemon.