The article wasn't what I expected because having read my share of Feynman I would totally expect him to have typed up that J Edgar Hoover memo by himself, signed it himself, and mailed it to the manager of the local FBI office just to see what happens.

I would be surprised if he's the first guy to try that.

The trick with social engineering people back in those days was getting the typewritten formats identical. Being Feynman all he would have needed was one actual memo to copy from and away he goes.