Black decides to postpone castling and this can lead to original play.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... d7d5  4. g2g3  4... f8b4  5. c1d2  5... b4e7  6. f1g2  6... c7c6  7. d1c2  7... b7b6  8. e1g1 