Adding Easter eggs to your application is a great way to reward your frequent users with a bit of a surprise out of the blue. Easter eggs allow you to have a little bit of fun with your user base without being too explicit.
The problem, however, is finding the right balance of fun and professionalism. After all, you still want to hold on to the hard earned respect your users give you for providing them with a high quality software application. Easter eggs that are too extreme, blatant, or political can end up having the opposite effect and create a negative experience for your users.
Here's a great example of an Easter egg that Last.fm placed in their robots.txt file.
User-Agent: * Disallow: /music? Disallow: /widgets/radio? Disallow: /show_ads.php Disallow: /affiliate/ Disallow: /affiliate_redirect.php Disallow: /affiliate_sendto.php Disallow: /affiliatelink.php Disallow: /campaignlink.php Disallow: /delivery.php Disallow: /music/+noredirect/ Disallow: /harming/humans Disallow: /ignoring/human/orders Disallow: /harm/to/self Allow: /
This is a very subtle and perfectly placed Easter egg that will likely resonate with the types of users that will go digging around in a site's robots.txt file.
You also get the added benefit of healthy discussion when your Easter eggs are discovered.
Next time you're looking for an interesting way to make your product stand out from the competition, why not let your users stumble on an Easter egg?