This is the first game I've taught my son. I introduced this to him when he was almost two years old. He thought the monsters were Cookie Monsters, so he says "cookie" whenever he draws a monster from the bag.
In the second video, he was 3 months older and was better at the game. But he still calls the monsters "cookie."
In the third video, he tried to cheat by peeking into the bag.
I taught this to my son when he was three. He had trouble playing this initially. So everyday, we practiced piling animals. First it was just with two. Then three. Then four. Etc. Eventually he got good with the game.
In this video, he is almost four, and his skills had improved.