"Why would you do that?!" she exclaims. Somehow, neither the question mark nor the exclamation point is enough to convey her emotion. We need a punctuation mark that combines inquiry and incredulity.
Back in 1962, Martin K. Speckter invented one. Speckter, owner of an ad agency in New York, suggested in TYPETalks Magazine a new punctuation mark to use in those situations. He called it an "interrobang," and it looked like this:
The trouble was, it was hard to use the interrobang. People had to type a question mark, back-space, and then superimpose an exclamation point. Typesetters had to handcraft the new mark. Finally in 1966, American Type Founders included the interrobang in its Americana typeface, and two years later, Remington Rand made the key an option on its 1968 typewriters.
Sadly, the interrobang never moved beyond the advertising world to become popular with the public. Both the literary world and academia questioned whether a new punctuation mark was even needed.
Today, you can find the interrobang in MS Word, where it's a character in the Wingdings 2 font and the Calibri font. Facebook also has a page on the topic.
The next time you want to combine incredulity and inquiry, consider the interrobang.