Google is well-known for hiding Easter eggs within its products and the new Hangouts is no different. There are at least six Easter eggs present in Hangouts that have been detailed by a Google+ user. You'll need to be using the desktop version of Hangouts on Google+ or the Chrome Extension.
Head on over to Google+ Hangouts and try these Easter eggs out. Some people have reported a few issues with the web interface for Hangouts, but these same reports say the Chrome app works flawlessly.