What a great interview question! I'm a big fan of anything that throw a candidate off, and this is exactly why I encourage every candidate to be ready for anything when it comes to both the case and fit portion of interviews.
There's not "right" answer here. However, there are plenty of "wrong" answers.
Any animal with a negative connation should be avoided (unless you can defend it). Snails, slugs, skunks, sloths, come to mind! Any mis-interpretation of the true culture/status of the company should also be avoided.
Essentially, this is testing whether you can think on your feet, "have fun", think outside of the box, and be clever/creative.