This is cute, pointed out in a tweet by Matt Cutts. There is a Halloween easter egg in Google's robots.txt file.
Disallow: /errors/
Disallow: /voice/fm/
Disallow: /voice/media/
Disallow: /voice/shared/
Disallow: /app/updates
User-agent: Kids
Disallow: /tricks
Allow: /treats
Sitemap: http://www.gstatic.com/s2/...