I should be
A British way to say 'I should think not.' Like you're so annoyed you're trying to rhyme everything. Also spelled 'I should co-co' or 'I should cocoa.' It's basically just a fancy way to say 'no way.'
I should be listening to you. I should co-co. I should think not.
I should be doing homework. I should cocoa. I should think you're stupid.
I should be being nice. I should co-co. I should think you're annoying.