From the first episode of Gochuumon wa Usagi desuka? (Is the order a rabbit?) Chino's grandfather was depicted as a rabbit (very questionable since he didn't look like a rabbit, but the anime says so, so let's call him a rabbit). However, considering that both Chino's father and Chino are normal humans, and that the writer who often comes to Chino's cafe (Rabbit House) used to chat with the first owner (Chino's grandfather), there must be a time where he was a normal human. Otherwise, the writer lady would have noticed it was him when she saw the rabbit. Also since the rabbit has no arms (at least the first season doesn't show it having arms), and considering his size, he wouldn't be able to pour coffee. Has it been explained somewhere (anime and manga) why Chino's grandfather turned into a rabbit?
Note: I haven't watched the second season. Please carefully put spoilers if they come up.