This is a great humourous Firefox Extension which gives different titles to your browser window, such as Powerjackel or Lightingporpoise. The plugin was created by Cosmic Cat Creations, not me. The main page for this extension can be found on Cosmic Cat’s site. However, it does not install properly on the latest versions of Firefox. I have modified the plugin simply by changing the compatibility checking, since the actual code seems to work fine up to Firefox 1.5.0.2. I have had no problems running it, but of course cannot guarantee the same for you.
To install: Download the file, then open Firefox and click File -> Open File. Find the firesomething.xpi file you just downloaded, and then click install. Comment here if you have any problems.
Edit: This extension now works with Firefox 3.0.