Programming thought experiments

I hope this question is allowed here, if not please delete or move!

Last year a colleague mentioned the 'Two Generals' thought experiment to me which has stuck in my mind ever since, especially as I had encountered the problem issue first hand when creating a real-time booking system and it had resulted in much head-scratching!

My question is, are there any other dev-related throught experements peolpe know of or is this a one-off?

Thanks