The Great Gatsby, wild wag of an oculist

In the use of "wild" in this extract from the second chapter of The Great Gatsby, is the denotation "zany"? Or does it suggests what is called "fly-by-night" type of business, one that is often called in Yiddish slang schlock, meaning cheap or shoddy in methods?

The eyes of Doctor T. J. Eckleburg are blue and gigantic—their retinas are one yard high. They look out of no face, but, instead, from a pair of enormous yellow spectacles which pass over a nonexistent nose. Evidently some wild wag of an oculist set them there to fatten his practice in the borough of Queens and then sank down himself into eternal blindness or forgot them and moved away.

Thank you.