RichThesaurus
not while pussy's a cat
vs
when Hell freezes over
not while pussy's a cat
adv
never
when Hell freezes over
adv
Never; not in this lifetime or a time in the unforeseeably distant future; not a chance.
How often have the words
not while pussy's a cat
and
when Hell freezes over
occurred in a corpus of books?
(source:
Google Ngram Viewer
)