During Act 1, you'll find yourself in front of a giant toad statue. You need to fail the puzzle to get the achievement.
Stand on the platform next to the toad statue. Jump vertically on the wooden platform twice -- on the second time, the platform will give way. Quickly sprint off the lower wooden ledge and hide underneath it. The toad head will come rolling past, the ledge will collapse and Teku will be squashed between the platform and the wall.