xkcd #3201: Proof Without Content
Title text:
There’s also a proof without content of a conjecture without content, but it’s left as an exercise for the reader.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3201/
I’ve heard it both ways.
It’s far more likely you aren’t a boltsman brain and that one has never existed.