A few of my colleagues were arguing (friendly argument) if the word "creature" can be used to describe people.
Yes the word "creature" can be used to described people...
According to Cambridge Dictionary http://dictionary.cambridge.org/define.asp?key=18142&dict=CALD
1 any large or small living thing which can move independently; an animal:
. Rain forests are filled with amazing creatures.
. Don't all living creatures have certain rights?
. Blue whales are the largest creatures ever to have lived.
2 used to refer to a life form that is unusual, unknown or imaginary:
. The unicorn is a mythical creature.
. The film was about creatures from outer space.
. The duck-billed platypus is a truly bizarre creature.
3 used to refer to a person when an opinion is being expressed about them:
. John is a strange/weak/pathetic creature.
. A lovely blonde creature (= a beautiful blonde woman) walked into the room.
Creature of Habit may refer to in Wikipedia http://en.wikipedia.org/wiki/Creatures_of_Habit
. one who is extremely used to their own habits and does not function well without them.