[ECO code C20]
The Hippopotamus Variation
Black develops his Queen to KR5(h4), attacking White's KP and pinning White's KBP+K. This line continues for a famous smothered mate by Black (the "Hippopotamus Game") in six moves. B-Alt.
White Black 1. P-K4 P-K4 2. Kt-K2 Q-R5
WHITE to or Undo or Jump or Clear