as it happens/happened used when you say something that is surprising, or something connected with what somebody else has just said I agree with you, as it happens. As it happens, I have a spare set of keys in my office. He doesn't mind leaving his script and reacting to whatever happens on the night.

Understanding the Context

But whatever happens, the only certainty is that the crags will never change. When something happens to someone or something, it takes place and affects them. I wonder what 's happened to Jeremy? If anything happens to the car, you'll have to pay for it.

Key Insights

In sentences like these, don't use any preposition except to after happen.