“If we could trigger a reward for every click we put in, would that cause people to continue interacting with it?” Ms. Ma wondered. It did.

A year later, Ms. Ma and Ms. Syam reused that template for an F.A.Q. about the royal baby watch. This time, rather than placing Easter eggs throughout, the designers decided to surprise the most diligent readers by changing the language to baby talk. (Hint: Read the very last question.)

Some of the Easter eggs that have made it to The Times’s site were hidden simply for the fun of it.

Ahead of the 2008 Olympic Games, the Graphics desk produced an interactive article that covered the history of Olympic torch design from 1936 to 2008. Using side-by-side photos, the interactive showed the evolution of the torches as shapes, materials and colors changed over the years. While hovering over the torches revealed details about each one, click-happy readers discovered that clicking on specific torches produced a deLIGHTful surprise. Hint: first, last and first again. (Note that the article will work only on computers with Flash installed.)

An article published in early 2018 about the demographics of dog registration in New York City featured a couple of visual treats, including animated illustrations of very good dogs. Although the Yorkie came out on top as the most popular pooch in New York City, the news designer Rumsey Taylor decided to give his own terrier mix, Sprout, a moment in the spotlight. “I just think dogs are great and wanted to add mine somehow,” Mr. Taylor said. Typing “Sprout” while viewing the page will play a recording of Sprout’s bark.

But perhaps what’s most notable about Easter eggs is that once they’ve been published, they’re quickly forgotten. Of all the current and former Times people I spoke with for this article, most said they could remember only vague details about the hidden messages they embedded in articles. By design, Easter eggs are meant to delight, if just for a moment.

Building Easter eggs into a project can be a way for a web developer or designer to infuse an often exacting and time-consuming job with a little whimsy. While stories like “The Yorkie’s Dominance” and “The Royal Wedding F.A.Q.” might seem simple, they most likely took days, if not weeks, to produce. “If you can make each other laugh,” said Ms. Ma, “it makes it a little better.”

The ideas for Easter eggs often start as conversations with colleagues and later become elements of the project. Sometimes they are a sneaky way to test out a design feature that doesn’t quite fit the narrative of the story. The lessons learned might then be carried over to future articles.