Occasionally - nothing.
If your dog usually/Always eat cat food it may not do that well since dogs and cats don't have exactly the same dietary requirements. Cat food has more fat and protein than dog food.
If it just happens a few times it shouldn't be a problem but cat food is high in protein so it could cause a dog to gain weight if fed on a regular basis.
Will do no harm, I have a cat that eats Dogfish heads.
It gets digested.
no. the only main difference between cat and dog food is that a dog food can contains preferably more meat than a cat food can. basically, if a dog eats cat food, there should be absoloutely no problem.
Life.
No. I used to have a dog that would eat nothing but dry cat food, and only Purina cat food. I later found out though, that cat food has a higher amount of protein than dog food, and could have resulted in health problems for my dog if I had kept him on it long term. But an ocassional meal of cat food will not hurt your dog.
Dog/cat food.
No.
It's all part of the grand design of the food chain: the bigger fish eats the smaller fish. The dog eats the cat. The cat eats the mouse. The mouse eats the grain. The grain eats nutrients from the soil. The soil is rich in nutrients because of a decomposing dog. Or cat. Or mouse, even. Thus, we can conclude: the worm is on top of them all in the food chain !
no
it eats anything out of the food bowl for the dog..
no they will not it only eats little bits of dog or cat food