|Please note that this is the D.GrayMan Encyclopedia's article on Allen, the dog of Mana Walker, if you are looking for the article on the main protagonist of the series then you should head to Allen Walker.|
Allen Walker/Red's friend.
Allen is a rather big dog of unknown race. His fur is mostly white with brown spots on the back and brown fur on the top of the had and the ears leaving a white fur line between the eyes reminding of a bone. He is dressed with a star-shaped ruff and a small round hat on the right side of his head.
Allen seems to be a friendly and not shy dog as he easily licked Allen's unusual hand just after meeting him.
Allen was Mana's pet dog who accompanied him on many circus shows. When Red (Allen Walker) first met Allen, Allen tried to befriend him but Red tried to stay away from him since Allen and Mana will leave one day and Red doesn't want his heart to be broken.
Cosimov (Red's arch-nemesis) wanted Red to feed Allen broken glass, since Cosimov hates Mana and Allen being more famous than he is. Red refused to do so and was beaten up.
One day, before a show, Red found Allen sleeping and looking ill. When Red get closer to him, he patted Allen
Later, Mana finds his dog and is soon joined by Red who asks him if the dog is dead. Mana nods and in the anime answers that he was an old dog. Red notices that the dog has bruises. Mana explains that he doesn't seem to be able to cry over his dog as "his tears may have dried up". Mana realizes that Red was Allen's friend as the dog cries. They then bury the dog.
After starting traveling with Red, with his sanity slipping Mana started mistaking Red for his late dog and called him by his name. Red eventually took Allen's name.
Disappearance of Cross Marian arc Edit
Allen Walker thinks of his encounter with Mana before the body of the dog when he is about to meet Cross Marian. 
Searching for A.W. arc Edit
Allen is seen in Allen/Red's memory in Nea's inner world.