I had no idea… thanks for pointing that out. Doesn't seem too useful for those of us that can see the comic for ourselves, but a nice easter egg nonetheless.
It's pretty fantastic for finding the xkcd strip you're thinking of via Google, since the comic transcripts are read by Googlebot.
Really cool feature. Thanks for sharing!
(Incidentally, did Randall not write a transcript for the latest comic 1216? I'm not able to find one yet.)