I can not.

I guess I've never really thought about it.

I can't not believe it isn't going to be the butter that was.

I can’t not believe its not butter.

Butter flavored plastic yum

Yes, because I cannot afford butter.

I refuse to believe it's not butter

I can not believe it, it's not true! It's baloney!
I can not believe it's butter! [throws a bottle on the ground in anger]
I can not! Oh, hi Jbone.