Several cartoons, video games, anime, and even kid shows have theories. But Arthur has never had a theory. I have a theory for the books and the cartoon. But this is depressing, if you get sensitive easily. I suggest you stop reading this. You have been warned. There once was a 8 year old boy named Arthur Read. He was a huge animal fanatic. Then one day in 1917, Arthur fell into a deep depression when his beloved dog, Pal, had been ran over by a car. Arthur was heartbroken. He couldn't cope with the loss of his best friend. In an effort to make him feel better, Arthur's parents took him and D.W. Read to the Elwood City Zoo (The city from the cartoon.)
The night before, burglars broke into the zoo. They made locks, barriers, and the bars very loose, to where they can break easily, in an attempt to cause harm to the zoo patriots, without it being noticeable that something was wrong with the animal cages and the barriers. When the Read family was in the Cats area in the zoo, the Lions were unusually close to the patriots. Too close, since the barriers were loosened by the burglars the night before.
The zoo patriots were freaking out. Then, the lions broke the barriers open! Soon the other animals broke free from the cages and barriers! The animals started rampaging, badly injuring the patriots. Some have even died. Arthur tried to escape but a male lion attacked him. The lion mangled him, clawed the back of his head, and left several gashes on Arthur's body.
Just as Arthur was about to die (or supposedly), he saw an aardvark coming to comfort him, much like his now deceased pet, Pal. The aardvark sniffed him and had a sad look on its face. Arthur smiled and collapsed due to his severe injures.
The Read family escaped and carried Arthur to the nearest Emergency room. The doctors discovered that he was still breathing. But they were unable to wake him up, as he was in a coma. Arthur dreamed that everyone was an animal, still humanoid-like as they were able to talk, walk on two legs, drive, read, and have minds of their own. It seemed like Arthur was reborn, into an aardvark.
His life started over from birth to death. Pal was reborn again and he never died from a car. The Read family were aardvarks because an aardvark was the last thing Arthur ever saw before he fell into a coma. Buster was a rabbit, while Arthur's other real world friends were bears, monkeys, cats, dogs, a moose, and even rats (including Mr. Ratburn.)
Arthur lived on through his dream. He graduated Lakewood Elementary (his school in the show), then high school, he went to collage, he got married to Francine Frensky, and they had a family together. At the end of the cartoon episode "And Now Let's Talk to Some Kids," Arthur and Francine (now old) are watching the Professor Brain show who was their childhood friend, who was a bear, and died of the flu in 1977 at age 76.
They then play an old tape which they appeared on a segment of the show "The Magic Tool Box." Francine says "And there is Buster Baxter. What ever happened to him?" Buster, unknown to Arthur and Francine had died of a heart attack in 1988 at the age of 79.
Arthur eventually dies in 1993 at age 84 of natural causes, while Francine dies in 2001 two weeks before her 92nd birthday, also of natural causes. Arhtur's dad died in 1948 at age 72 of pneumonia, while his mom died in 1959 at age 85 of an aortic dissection. As for D.W she lived Arthur's legacy until her death in 2006 at age 93 due to heart disease, as for Baby Kate she didn't live as long, she died in 1935 at age 19 due to breast cancer.
Arthur never woke up from the coma, breaking a world record for being in a coma for 76 years! All this time, the books and the cartoon were all an 8 year old's dream while in a coma. Arthur may have not got a chance to live in the real world, but lived a good life in the dream world. He became a successful man writing books and a cartoon show based on his life. In the dream world that is...