Easter eggs in media such as computer games, software design, and movies are hidden messages or inside jokes that only people familiar with the particular type of media will get.
But do Easter eggs exist in romance novels?
We went to Twitter, and the answer is yes! Larissa Ione has several mentions of Star Trek (she is a big fan), Maisey Yates has a heroine from one (unconnected) book come from the fictional hometown of another series, while Sherrilyn Kenyon mentions a Kinley MacGregor (her historical alter-ego) book in one of her Kenyon releases. And there are many more examples.
Have you noticed any Easter eggs in romance? What ones did you spot?