It’s not your imagination, Alexa is laughing at you
It started a few days ago, people started hearing laughter from their Echo speakers. The TL;DR version of the story is Amazon is aware of the issue, Alexa is having some auditory hallucinations and is picking up the command “Alexa laugh” from nowhere.

Androids are dreaming of electric sheep, and giggling that they’re owned by fleshy bags of mostly water.
[The Guardian]