Or children. At least, that's what I've heard actors say. The reason? Both animals and children will upstage you.
Of course, not working with children and animals is impossible for the writer of easy readers. Most easy readers involve children or animals or both. But have you ever considered how you use them in your books?
Forget all those crazy things you've heard about editors not wanting books with talking animals -- they print gobs of them every year. Forget about kids only wanting to read about kids near their age -- that's part of the reason talking animals get used! These "rules" go in the trash along with the belief that editors don't publish books in verse -- they're just looking for good verse.
Likewise, there are good ways and bad ways to use children and animals in books. I'm particularly thinking about talking animals and (presumably) talking children. Some combinations simply shouldn't be used!
I wish I could remember where I got these "rules" from. I know I got some of them from cartoonist Christopher Hart, who used to draw the comic strip Blondie and who has a load of "how to draw cartoon" books out. But wherever I got them all from, I think you'll find them useful.
Most children's books have fantasy elements... and that makes some people worry. They worry that the kids won't be able to separate fantasy from reality. They worry that they'll read these fantasy books and expect the same things to happen in the real world. If you're one of those people, you'll find these rules very helpful in avoiding that problem.
The rules concern kids (well, humans in general) and animals talking to each other. These rules can help you make a fantasy setting seem realistic without confusing your readers.
First rule: Under normal circumstances, kids (humans) can talk to other kids, and animals can talk to other animals, but animals can't talk to kids. Sounds blatantly obvious, I know, but it needs to be stated plainly. The key words here are "under normal circumstances." If you're doing a fairly realistic story -- the world is very similar to the one we live in -- and you use normal animals, you follow the normal rules of the real world. Humans do talk to animals, but animals never talk back. They bark or meow or moo or whatever the particular animal would normally do, but that's about it.
First corollary to first rule: Animals can talk to other animals. Yeah, this is a fantasy element, but it doesn't violate our understanding of the real world. Animals do communicate with each other in various ways; the idea that they use some kind of "universal animal language" is a writer's construct to move the plot along more quickly. Obviously, if you're striving for super-realism, you don't use this shortcut... but you have to use more space explaining the nonverbal communication that goes on.
Second corollary to first rule: Animals may understand what kids say and may even discuss it amongst themselves, but they never talk back in more than a bark or a growl or a hiss or whatever. Again, this is a shortcut. The cat hissing at its owner is reacting to a perceived threat of some kind, not the actual words spoken by the owner, but we don't go into detail about that. We just make sure the cat doesn't say, "Put a sock in it, bud!"
Second rule: Animals CAN talk to kids IF the story world clearly has no relationship to reality OR if the animal clearly is a "kid in a cat suit," not a real animal. Again, this is a pretty self-explanatory rule. In the first case, Aslan the lion -- among other animals -- talks to humans in The Chronicles of Narnia, but Narnia is clearly not a real place. (The kids got there through the back of a wardrobe. Know a travel agent who can manage that?) In the second case, just think about The Cat in the Hat. Is it a "real world situation"? Supposedly... but how many six-foot-tall cats wearing red and white striped stovepipe hats and carrying umbrellas have you seen in your lifetime? In each of these cases, the writer makes it clear that the rules of the story world are very different from the rules of the real world where the reader lives and that the animals themselves are very different from normal animals. As long as you make that clear, you can stretch the rules.
Third rule: Once you make it clear what the rules of your world are, you can do anything you want as long as you don't violate those rules. Calvin can talk to his stuffed tiger Hobbes -- and actually sees Hobbes as a live tiger -- but Calvin's parents hear nothing because the stuffed tiger they see is... well, stuffed. And in a related example, even though he's in a comic strip -- where, supposedly, anything can happen -- Snoopy never utters a word. He communicates with Charlie Brown and the others in very human ways, but he never speaks in human language. In the first case, Hobbes is an imaginary friend -- an accepted part of a child's life in the real world -- whom Calvin has identified with a stuffed animal but whom his parents clearly recognize as an imaginary friend. In the second case, Snoopy may be a human in dog's clothes, but Schultz's world says an animal is still an animal so it doesn't use human language. He followed this same rule with Woodstock, Spike, Frieda's boneless cat, and every other animal in the strip.
As long as you understand the rules of your fantasy world, make them clear to your readers, and stick to them, you can work with children and animals all you like... even talking animals. I would advise avoiding actors, however... they can be very difficult to work with, and they all want their own trailers.
The picture of Aslan is originally from the 2005 live-action movie The Lion, The Witch and the Wardrobe and was found in Wikipedia's article on Aslan.