My game just tried to unlive me for no reason

Ha ha ha...  sometimes this game behaves so strangely.   I was helping my wife in the game by buying her a rocket ship launch pad while she was sleeping.  Suddenly my sim started laughing hysterically.  Why?  I have no idea but then I died.  what a way to start your day.  Well,  that didn't make any sense.  So I just exited and restarted from an earlier save and escaped death.  But I am still puzzled about why any sim would laugh about just buying a rocketship?  It isn't funny.