who knows what
see under what have you.
Examples from the Web for who knows what
Like mushrooms, in a single sight we spring up—a pen in our hands, very little in our brains, and who-knows-what in our hearts!The Complete Essays of John Galsworthy|John Galsworthy
The little model gave him a look with who-knows-what of reproach in it, and, faithful to her training, went submissively away.Fraternity|John Galsworthy