Good small pets

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So I just moved out of my parents house, and although my university won't let me have a pet, I know I will be buying my own apartment eventually. I love dogs, but recently I've been toying around with the idea of having a different pet, something like a hamster or a flying monkey. I've also heard that rats make good pets. I just want something that is friendly, and not any more work than a slightly demanding lap dog. Do you guys have any ideas for good, atypical pets? Or am I better off just going to the humane society and picking the cutest animal I see?