I need that like a moose needs a hat rack

I need that like a moose needs a hat rack is another way of saying you dont need something in such a way that it is both severe and comical in the way the expression is said. If someone hears that you need something like a moose needs a hat rack, it will be plainly obvious to them that you dont need what is being offered to them. A mouse certainly does not need a hat rack, therefore you have your answer.