a right one

we've got a right one here

A set phrase used to humorously indicate that one has encountered someone or something they consider stupid or foolish. You think the moon is bigger than the Earth? We've got a right one here!
See also: here, one, right
Farlex Dictionary of Idioms.

a right one

a silly or foolish person. British informal
1988 Salman Rushdie The Satanic Verses Quite soon they burst out into uproarious guffaws, we've got a right one here and no mistake.
See also: one, right
Farlex Partner Idioms Dictionary
See also:
  • how the mighty are fallen
  • how the mighty have fallen
  • and I don't play one on TV
  • as you do
  • are we having fun yet
  • Are we having fun yet?
  • AWHFY
  • and a partridge in a pear tree
  • believe it or not
  • bion