There are still places for good easter eggs.

In a past life I did technical writing and slipped all sorts of fun things into my documentation: Multiple 4/20 references, my birthday, in-jokes from the team that I was working with, even the occasional proper meme. When I needed a link? Something funny from the official corporate channel on YouTube that I could get away with. Needed a company name? I checked every trademark we had on file to find Something.

Never be afraid to hide something wonderful in your code. The header for UFS2 contains the author's birthday [0] and OpenVMS has several interesting exit code states [1]

[0] https://en.wikipedia.org/wiki/Marshall_Kirk_McKusick [1] https://www.parsec.com/os/openvms/undocumented.php?page=13