a new one (on me)
Something I was not aware or informed of or knew nothing about until just now. A: "Yeah, Jeff and Anthony have been going out for a few months now." B: "That's a new one—I thought they were just friends." Having to pay for the water you use in your house is a new one to me—is that an American thing or something?
new one on someone something
that one has not heard before and that one is not ready to believe. Bob's talk of poverty is a new one on me. He always seems to have plenty of money. The firm's difficulties are a new one on me. I thought that it was doing very well.