Is it like this: "Where are my slippers!?"
Or is it like this: "Where are my slippers?!"
Is it like this: "Where are my slippers!?"
Or is it like this: "Where are my slippers?!"
An exclamation mark and question mark used together are collectively known as an Interrobang in typsetting conventions. You can use them in either order, according to the Wikipedia entry. This less than reliable source is backed up by Mirriam-Webster, which says:
Most punctuation marks have been around for centuries, but not the interrobang: it's a product of the 1960s. The mark gets its name from the punctuation that it is intended to combine. Interro is from "interrogation point," the technical name for the question mark, and bang is printers' slang for the exclamation point. The interrobang is not commonly used-its absence from standard keyboards can explain its paucity in print perhaps just as well as its paucity in print can explain its absence from standard keyboards. Most writers who want to communicate what the interrobang communicates continue to do as they did before the advent of the mark, throwing in !? or ?! as they feel so moved. (emphasis added)
The Copy Curmudgeon has a whole post devoted to which order is to be preferred, and concludes:
So when one or the other just won’t do, it’s fine to use both an exclamation point and a question mark in casual writing, and it makes no difference what order you use them in.