Attached to an animal prefab. For the "Many Game Objects from One Prefab and an Array of Sprites" tutorial.

Animal.cs

using UnityEngine;
using System.Collections;

public class Animal : MonoBehaviour {

	private Vector2 origPos;
	public string animalName;
	public bool returnToOrigin = false;

	void Start () {
		origPos = transform.position;
	}

	void OnMouseUp() {
		if (returnToOrigin)
			transform.position = origPos;
	}
}