The four executions, which break this week, continue to differentiate the chocolate from the competition by focusing on its superior taste credentials.
Fallon was briefed to inject a personal touch into the campaign in order to build a more intimate relationship with consumers.
One of the ads, for the brand's vanilla chocolate variant, pictures a bar of the chocolate along with the words: "There's no such thing as the vanilla flavouring harvest, that's why we prefer to use the real thing." The endline reads: "Green & Black's organic. What chocolate's supposed to taste like."
The ads were written and art directed by Ed Edwards and Dave Masterman.
Media planning and buying was handled by Unity.
The work will appear on 6,000 London Underground Tube card sites for the next two weeks.
Mark Palmer, the marketing director at Green & Black's, said: "Our aim is to make real chocolate the norm rather than the niche, encouraging commuters to rethink their expectations of what chocolate should taste like."