Each player chooses an animal to be during the game, and decides on both a noise and an action that they'll do for that animal. For example, a player might choose to be a parrot whose noise is a squawk and whose action is flapping your arms. Players should try to pick funny noises and actions to make the game interesting.
The game begins after everyone has decided on their animal and told the other players what it is. The first player starts by making their own noise and action, followed by the noise and action of another player. Play then passes to that player, who must do the noise and action of the first player, their own noise and action, then the noise and action of any other player (including the first player). Play then passes to that player, and so on.
The first person to make a mistake or hesitate for too long must down their drink. If you're finding the game too easy you can introduce an extra rule - anyone who laughs must take a drink.