That’s a new one on me

that's a new one on me

That is something I was not aware about or did not know. A: "Yeah, Jeff and Anthony have been going out for a few months now." B: "That's a new one on me. I thought they were just friends." You aren't allowed to dump your grass clippings here? Well, that's a new one on me.
See also: new, on, one
Farlex Dictionary of Idioms.

That’s a new one on me

sent. That is truly amazing.; I did not know that. A talking camera? That’s a new one on me.
See also: new, on, one
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • (I) hope not
  • hope not
  • not for a second
  • not for a minute
  • not for a moment
  • aint
  • ain't
  • not (one's) long suit
  • not for a instant
  • not for a/one minute/moment/second/instant