You Can’t Make This Stuff Up

What does the expression “you can’t make this stuff up” mean?

Definition: what has happened is so unlikely that there’s no way I could even have imagined or invented it

Example: So, I’m late because the bus was delayed, the train way delayed, and a taxi strike started, all at the same time. You can’t make this stuff up.

Note: “You can’t make this shit up” is an obscene variant.