What if you could take any living thing from a book or movie and summon them to earth?
In my opinion I would choose an animal with a binding contract to me. Because humans are too unpredictable and most living forms from different worlds would not be happy about being summoned. Thus if I had a binding/loyalty contract with me as the master, not only would I have control over the creature I summoned, but also a companion. As for what kind of creature I really don't care, I love all animals. But to keep the world and summoned creature safe. the animal I would summon would have to be a herbivore that can eat earth plants.
But alas it's only a thought by an avid otherworldly genre reader/watcher fan.