You know what it looks like… but what is it called?
TAKE THE QUIZ“can't be”
The following 2 entries include the term can't be.
beggars can't be choosers
idiom—used to say that people who need something should be satisfied with what they get even if it is not exactly what they wanted
can't be serious
idiom—used to express disbelief about what someone said
Love words? Need even more definitions?
Merriam-Webster unabridged