This is very simple. You need to look to the three bears standing up on the first two levels of Tomb Raider 1.
On "Cave", after the rope bridges sectin, there is a gap. On this gap we have the fisrt bear. Dance with it until it gets up on it two legs. You just need to sse it, no need to use the look button.
On "City of Vilcabamba", after start the level, go left, kill thye wolfs, get to the water, turn right and enter in some kind of stable. There is our second bear.
On the last section o "City of Vilcabamba", just before the level exit we find the last bear. After you watch all three getting up and walking on two legs, the achivement should pop.