The Girl Genius Complete List of Absolutely Everybody is/was an incredibly valuable resource set up by the Professors Foglio on the main Girl Genius site; URL http://www.girlgeniusonline.com/info/cast/everybody.php. As hinted by the name, basic information on the overwhelming majority of characters in the story appear there. It's sometimes called GGCLAE for short.
The GGCLAE has come and gone in terms of Internet availability over years. If it is currently among the missing again, a version is available from the Internet Archive Wayback Machine: http://web.archive.org/web/20080212023400/http://www.girlgeniusonline.com/info/cast/everybody.php
The GGCLAE isn't quite perfect. Its information is now several years out of date, not everyone has their portrait included, and there are a few misspellings and such. For example, the old guy who's Seneschal Emeritus for House Heterodyne appears as Carson von Mekkhan in the , but the spelling in the GGCLAE is von Mekkahn. On the other hand, it has listed some "canon" folks who even now are yet to appear in the main comic, such as Princess Urania of England.
It has been officially replaced with cast lists for the individual volumes in the series; currently the site has:
Note that copying text lock-stock-and-barrel from the GGCLAE into articles here is absolutely forbidden, just as it is from any other copyrighted source. Unlike things in this wiki, material appearing in the GGCLAE is copyrighted and cannot be re-used (except in brief excerpts for "review" purposes) without the authors' permission. If you're planning on writing an article here on someone covered in the GGCLAE, use your own words and ideas, not the Foglios'.