Google Voice - When typing an SMS, the counter changes to “Really?” when your message reaches a certain lenght.
Google Images – When dragging a photo on the page or into the browser, the search input changes to support drag’and’drop.
Google - Google wishes you happy birthday based on the information from your Google+ profile. Clicking the doodle sends you to your profile at Google+.
/via Alexey Gornostaev
Google street view - The icon changes to a skier when viewing a piste. Try picking it up as well.
Google Translate - When translating a beatbox sound in German, the “Listen” button automatically changes into “Beatbox!”.
WDYL.com - When searching for a dirty word or phrase, instead of giving a safe-search error the website shows results for the word “kittens.”
/via Zachary Reese
Google URL Shortener - After shortening a link the shortened link is automatically selected.
Google+ - Clicking on someone’s profile picture makes it flip around to show previous pictures.
/via Alex Popov
Google Calendar - Favicon displays the day of the month.