I worked for a company where a developer put a dirty limerick in a UI control, activated by a keystone sequence.
They also turned on output tracing via another keystroke sequence.
During a presentation, one of the consultants needed to turn on tracing in front of a VERY large multinational client (heavens knows why, it was in front of C-suite execs…). They hit the wrong keystroke, and up popped the limerick - on a large projector, in front of the CEO.
I'm not saying putting easter eggs in is a good practice, only that it's not rare. I think with pretty much every company I've worked for, putting in easter eggs was specifically forbidden. And, in every company, they were put in anyway -- they just had to be sneaky enough to pass through code review undetected (which, I think, improved the quality of them!)
I don't think software is capable of wanting anything. As a FOSS user the less "seriousness" the better. Life is just more fun with jokes. I love that I can build "sudo" with an option to have it insult me when I get my password wrong. Who wants to live a serious life?
It's a criticism of the way FOSS software advocates seem to want to eat their cake and have it too. They ask the world why they aren't using more FOSS software, which has all these benefits from being free and open, and when the world replies with a list of all the downsides of relying on software written by people hacking in their spare time --see: JWZ and the CADT model-- the advocates fall back on the defense that you can't complain because it is free.
I know it sounds ridiculous, because free software is written by a diverse group of people with diverse goals, but this conversation happens all the time because its advocates often try to represent it as a cohesive whole, that it very much isn't, in pursuit of their own agenda.