1
general::
Phrase(s): Of all things!
Can you imagine?; Imagine that! (Usually said about something very strange.) • She wore jeans to the dance. Of all things! • Billy, stop eating the houseplant! Of all things!
McGrawhill's American Idioms And Phrasal Verbs
2
general::
From all the possibilities, as in I said I'd help in any way I can, and of all things they want me to handle publicity. This term, generally expressing surprise, was first recorded in 1925.
American Heritage Idioms