I have the Urban Dictionary’s word of the day (which is often a phrase) drop into my inbox every morning. Here’s today’s:
February 17: that’s crazy
It’s the perfect response when you haven’t been listening at all.
It works whether the other person has been saying something funny, or sad, or infuriating, or boring….
(disclaimer….I’ve heard other people say that, but not me….)
27th Street 
I think Elvis used to say that…in some of the film clips at Graceland he said that’s crazy.
I don’t usually say “that’s crazy” but I have been known to utter, “crazy, man”.
That’s too funny. I say it all the time, but not for the reasons in the definition! I usually mean it!
I have heard that said.
Quite a lot actually.
No idea why.