Fairy-wrens often have other birds laying eggs in their nests (a brood parasite). They have adapted by singing a special tune to their eggs. Once hatched, those that sing the password get food while any brood parasite chicks go hungry. – WTF Fun Facts
tune
WTF Fun Fact – Curiosity’s Happy Birthday
In 2013, NASA’s Mars Curiosity rover hummed Happy Birthday to itself by vibrating its sample-analysis unit to the musical tune, but did so only on its first “birthday”. – WTF Fun Facts
Source: https://www.theatlantic.com/science/archive/2017/08/why-the-curiosity-rover-stopped-singing-happy-birthday-to-itself/536487/