Amazon is aware of the issue. There is a fix coming. However, until you get your Alexa fixed, you may get creeped out by her random laugh.
It’s not known if the laugh was coming after a command, or if it was simply a random case, but Alexa users have been surprised by the creepy very-human sounding laugh.
Amazon has come up with a fix for the issue. It involves disabling certain commands and replacing with simpler wording because her software is less likely to have an issue with similar common words and phrases.