My bunny eat my kitten's food, is it dangerous?

no the bunny should not eating cat food. Though an occasional theft likely won't hurt it, cats should be eating cat food and bunnies need to eat vegetation. I did have one that used to snitch a bit of doggie kibble here and there. Can't tell you why some seem to like it. You do need to find away to keep the bunzle away from the kitty food.