This amusing anecdote comes to mind: https://www.youtube.com/watch?v=2fsUAdlzwAs
Bearing risk in mind, there's probably a reason that it's acceptable to implement the DVD logo on the front-end client but poor taste to humorously update HTTP headers, for instance.
(That said, I tend to stay in the camp of "any path that can be hit, I'll eventually have to support.")
I am pretty sure easter eggs were a significant part of what made Google a cool company 10-15 years ago to my young eyes. The answer to life, the hidden games in Android, the raptor game in Chrome. At the time, it was rare for public company to do those silly things.
When that went, it was a sign google was different to the early days.
Who's to say it's not an internal training exercise? Someone(s) is learning to heard the kittens on a low-stakes project, someone else is learning to get the right sign-offs from the right teams/people, and the new test manager can spin her team up on this little project while they try the new workflow. And the intern gets to see their CSS tricks go into production to amuse millions.