The noun whatnot, meaning unspecified assorted objects or material, is one word. The phrase and whatnot carries essentially the same meaning as et cetera or and such, but whatnot is more informal, and it might be considered out of place in formal writing.
Whatnot has a second definition—a portable stand with shelves, used to display ornaments—but the word is rare in this use.
As Mike Tomlin pointed out yesterday, many of those released missed a lot of time anyway because of injuries and whatnot. [Pittsburgh Post-Gazette]
But this choice is connected to … his view that the current fashion in men’s clothing is so horrible – saggy denim and whatnot. [Sydney Morning Herald]
I know the convention with fantasy parties is to say you’d have Mandela and Hitler and whatnot. [Guardian]