Spook/Spooky is a common name for black animals, especially cats. Spook earned her name, though.

Isis I found is a common name for cats as well. She's picked up a few nicknames since we've had her though such as Spicy cat, Space ball and a few others that aren't too terribly polite.

Not sure how many hamsters (or other critters for that matter) are named Rodney but it seemed to fit his personality so the name stuck.