What is the name of the fictional universe that XXX is from?
Bat-Mite
After this, only three more Bat-Mite stories were published in the pre-Crisis DC Universe: two Bat-Mite/Mr. Mxyzptlk team ups in World's Finest Comics #152 (August 1965) and #169 (September 1967) (which were not edited by Schwartz but by Mort Weisinger), and ``Bat-Mite's New York Adventure'' from Detective Comics #482 (February--March 1979), in which the imp visits the DC Comics offices and insists that he be given his own feature in a Batman comic.
DC Universe