To have it you must give the dogs some zombies until they are full. The dogs will eat if you kill the zombies in front of then or their shadows.
The first dog is next to the B23R in the center of Mob of the Dead.
The second dog is next to the door which you find after using the gondola.
How to get the Bloondergat for free:
First you must get the Hell's Retriever. Then you must fly the plane to the Golden Gate and kill yourself in the electric chair. Now you must get 5 skulls in the following places:
How to get the golden spoon:
First you must kill yourself in the electric chairs that are on the Golden Gate after getting the Hell's Retriever.
After that you must throw the Retriever at the poster in the cell in the hall that leads to the Warden's Office.
Then you must use the Afterlife to get in the wall portal behind the cells and you will electrify a skeleton on the ground.
Now you must get a spoon in the cafeteria with the retriever.
Then you go to the bathroom and put the spoon in the bathtub.
Finally you only have to kill zombies in the showers until you hear a laugh. You go to the bathroom and get the spoon.