(as) busy as a hibernating bear
Not busy at all; inactive. He says he has no time to help our charity, but I know that he's off from school right now and busy as a hibernating bear!
*busy as a hibernating bear
not busy at all. (*Also: as ~.) Tom: I can't go with you. I'm busy. Jane: Yeah. You're as busy as a hibernating bear. He lounged on the sofa all day, busy as a hibernating bear.