Chess Opening Theory/1. e4/1...e5/2. Nf3/2...d6/3. d4/3...Nd7/4. Bc4/4...Ngf6

4...Ngf6
Like in 3...Be7?, this natural move loses a pawn, though not instantly. 4...exd4 and then only followed by Ngf6 is preferable. The only move that wins a pawn is 5. dxe5. The Hanham variation with 3...Nd7?! is full of traps, which is why 3..Ngf6 is more common. The simplest move order can lead to catastrophe.