The creature in our yard

My sister was in town last week and she playing in the backyard with Derek. All of the sudden Bella starts barking like crazy! There was a HUGE possum hanging out on the back wall. Sara was so funny... she made Derek and Bella come inside and lock the doors... as if the possum would really follow them inside and open the door if it wasn't locked! I went out to take a picture of it and Sara freaked out again. Saying that the possum might come jump at my face! It was SO FUNNY! Derek had no idea why this big animal was on the wall and he wanted to go outside to investigate so bad. But his protective Aunt Sara would not allow it!