That is a function of EnderZoo, if I remember correctly. It can be disabled in configs.The best/WORST thing I've seen is Ghast picking up random mobs and dive bombing you. As for the jokey riding chickens I have seen them lay eggs before. In ReGrowth that is, I killed a baby zombie and then led the chicken to a pen and it started laying eggs a few days later. However that could have been a Botania thing, because it was also dropping feathers and I could breed it.