This is what really fucking bored electronics folks do. (clicky)
...more of 'em. I've done innocuous additions myself (company logo, skull and crossbones). But one day, I'll add a giant cock-n-hairy-balls pic on a chip on tapeout when no one else is looking.
The Goal: Slack
The Method: The Casting Out of False Prophets
The Weapon: Time Control
The Motto: "Fuck 'em if They Can't Take A Joke"