when i saw the title, this quickly came in my mind,lol
By the way, thanks for sharing this.
The Four Knights, with its tranquil continental (i.e. Spanish, Scotch and Italian) continuations - unless, a brave soul dares to venture on to the Haloween Gambit (Nxe5?!) path! Interesting association, AncientChess - shall we rename it 'The Butterfly Οpening' ?
The Butterfly Variations