that's a new one

that's a new one

That is something I haven't heard before. Usually in reference to an unusual excuse or explanation, often said sarcastically or ironically. She said she couldn't turn in her assignment because her parakeet flew off with it out the window? Well, that's a new one. That's a new one—I've never heard of someone asking not to be paid for their overtime work before.
See also: new, one
Farlex Dictionary of Idioms.

new one

see under that's one on me.
See also: new, one
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • a mystery to (one)
  • a turn of phrase
  • a piece of the action
  • a piece/slice of the action
  • appear to
  • able to do
  • able to do it
  • a change of heart
  • a bit of the action
  • bit of the action