When you spawn choose any of the animals to be, go towards into the town where all the buildings are, on the left-hand side of the town you will find a chicken fast food type place with 3 people outside, if you go next to the people they will give you a mission to get them a boom box. The boom box can be found by heading south from the chicken place, then take your first left and the gym is on the right-hand side of the road about half way up the street. Lick the boom box to pick it up and take it back to the people and as soon as you get back to the people your achievement will pop.
If you need any more help or would like a video to direct you I will leave my video guide below.