how about that?

how about that

That is very interesting, impressive, exciting, surprising, or respectable. Said as an exclamation, rather than a question. A: "I heard Janet is running for a seat in the senate." B: "Wow, how about that!" How about that. Have you ever seen such a thing?
See also: how, that
Farlex Dictionary of Idioms.

how about that?

Isn't that surprising, remarkable, or pleasing. For example, They're engaged-how about that? [Colloquial; first half of 1900s]
See also: how
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • hoo-rah
  • atcha
  • back at you
  • back atcha
  • ah
  • be still my beating heart
  • be still my heart
  • manual