If I remember right, there are Java Easter eggs distributed throughout Android.
Completely Identical code with the comments removed. . . plus easter egg code that does nothing except provide flags that it was written by Oracle.
Similar code was hidden in Apple's Quicktime which included one of Apple's engineer's mother's maiden name and his social security number, resulted in Microsoft settling with Apple in their copyright and patent infringement suit in 1997. . . the suit that people keep claiming was Microsoft bailing Apple out with a $150 million investment, but that preferred restricted stock purchase was actually just one of the factors in the settlement agreement. Forensic Accountants auditing both companies' books years later came to the conclusion that the actual cost to Microsoft for pirating Apple's IT in Microsoft's Video Codex was almost $2 Billion, money that Apple was able to use for R&D to develop the iPod and iPhone.
I was using a Rand McNally map of San Francisco once which showed an Alley. . . and it simply did not exist. I called to report the error. . . and was informed they were quite well aware of that non-existent alley and was told they put it there deliberately. It's a deliberate error, I was told.
Rand McNally maps used to include non-existent streets and alleys on their maps as proof that another map maker had infringed their copyrights in their maps. . . On national and world maps there will be a non-existent river, mountain, city or town somewhere. . . and AT&T Yellow and White pages includes non-existent businesses and names/phone numbers for the same purpose. If those streets, alleys, rivers, cities, mountains, businesses, and names or phones numbers appear in someone else's products the publisher of the original has prima facie proof of copyright infringement and the copyright owner could sue and win!
Rand McNally actually wanted people to know these "ringer streets" existed. . . but would not let people know where they all were because the purpose was to discourage counterfeiting of their products! If you found one and called, they'd explained the fakes.