The line "Four legs good, two legs bad" quoted by Agent McNally is from George Orwell's Animal Farm. The slogan is a simplistic recap of the Seven Commandments of Animalism.
Mateo Pena is explaining using the lightbulb camera and an earwig so an accomplice can give him instructions. Sherlock calls the accomplice 'Cyrano' and Mateo doesn't get it. Cyrano de Bergerac is hidden and whispers clever and endearing lines to the dull witted cadet Christian as that twit tries to woo the beautiful and intelligent Roxanne.
The pistol mentioned is FÉG PA63. It is Hungarian made and is still used by the Hungarian Police.