You slowly bend forward as the pressure in the back of your cargo pants gets larger.
You look over at the other boy who is already hunched over, the lump in his pants growing ever larger.
You both start to pant. With each breath, you feel the lump grow tighter and tighter. As the growth gets bigger, it forces you to bend more and more forward.
You hear a ripping sound and the boy falls to all fours, a tail growing from his torn shorts, his shoulder length hair and donkey ears wet with sweat.
With a final grunt, you too feel the pressure burst from your pants. Your new tail quickly grows to full length as you pant, now on all fours. You look at the boy and then back at your own tail, wondering what will happen next.