Aye, it happened to me some yonks ago when we used to employ my entirely loveable nephew as a baby squasher.
One morning after a night before, I discovered the wonderfully titled self-replicating "Achtung! Sex Party" dialler all over the computer, including a robust presence on the desktop, potentially linking to a mega-premium dial-up number, had we not been on cable modem.
As I recall, he did say his goodnights and leave promptly that evening...