Through the looking glass

In the exerpt below from Lewis Carroll's Jabberwocky, each character is contained in its own GIF image. The set of character images was produced by running the GF2GIFs program against a backwards version of Donald Knuth's Computer Modern Roman font.


In Exercise 15.5 (and its solution) of the METAFONTbook, Knuth himself explains how to use METAFONT to produce mirror images of METAFONT picture variables, which is how this special backwards font was produced.