Cinnamon is a male cat living onboard the Lady Mercury as Thom's pet. Reportedly, he dislikes zero-g, the smell of gravy, and Reiko. He is an orange tabby, and is roughly 6 years old. He is slightly overweight for his age, but otherwise lives a comfortable and healthy life.
Very little is known about Cinnamon's past, although Thom has confirmed that he found him as a stray and took him in. The circumstances surrounding this are, again, unknown. It is often speculated that he is named after the spice of the same name, which is a rare and expensive commodity among alien species. This has neither been confirmed nor denied.
Cinnamon greatly enjoys exploring the Lady Mercury's living quarters, as there are several small tunnels and such that are accessible only to him, giving him full access to the ship (even past locked doors). He also enjoys spending time with Orog, whose scented smokes help him sleep (Cinnamon's favorite passtime), and Elliot, for reasons largely unknown.
Unofficially, Cinnamon "looks after" the ship when most of the crew is out. While most people take this as a joke, Thom is quite serious - he trusts the ship with Cinnamon almost as much as his own children. Contrary to his typical lazy nature, Cinnamon is very conscious of the ship's condition, and is often the first to notice if something is going wrong. If he senses something is not right, the first thing he'll do is alert a member of the crew (typically Thom or his sons). Cinnamon is credited with saving the ship from disaster on more than one occassion, one instance involving a potential meltdown of the ship's core driver.