How we lecturers set a course syllabus

In a conversation between me and another lecturer, said other lecturer being known worldwide in the field that is the very topic of this course, and also the organiser of it:

Me:

Thanks for agreeing to swap that lecture with me. I'm relieved not to be teaching that particular topic, because although I've a fair bit of practical experience with it, I don't know anything about the theoretical side of it and what the main issues are.

Other lecturer:

But you were the one who added the topic to the course, new for this year. I don't know much about it either.

Me:

Hey, it wasn't me who added it to the course, you're the organiser, you know about these things, you must have done it! Besides, I didn't even know what that acronym stood for, I had to look it up!

So how that topic got there, we have no idea. There wasn't anyone else involved in setting topics for the course. It must have wandered in of its own accord. Still, I don't mind, even if the swap did involve agreeing to write the exam questions. It's a fun topic, and I'm sure the students will enjoy it, because it will involve one of their favourite forms of bunking off.