For those who don't know the term, an Easter Egg is a reference to another piece of media within the piece of media you are currently viewing. It can take almost any form, from a subtle nod towards the source material to a really easily recognizable reference. It's just meant to be a hidden surprise (hence the name), and can be a fantastic way of appealing directly to your audience without actually breaking the forth wall. The Witcher series actually excels at this and while there are a huge number of Easter Eggs in the games, the games themselves are large enough that they never feel like they're happening to often.
So it's not exactly a secret that I'm crazy excited for The Witcher 3: The Wild Hunt. Seeing all the reviews start to come out is exciting, though I'm carefully avoiding any of the actual content of those reviews and just looking at scores. Which all rock by the way, it's getting very high 9s and even 10s. Normally though I would say that the scores are the least important part of the reviews. You want to find out WHY the game the game is good and not some arbitrary score it's assigned. In fact, it's important to note that when you're looking for a job as a designer and they ask you for your opinion of a game they are looking for why you think what you do rather than what you think. Telling them "the game is good" is useless.