The Passenger is simply along for the ride. It has no authority and no responsibilities on board the Torch, and simply wanders the halls looking for ways to entertain itself.
The Passenger has no department head. As such, the Executive Officer is responsible for ensuring that they stay out of trouble.
The Passenger role is entirely roleplay-based, with absolutely no mechanical advantages, responsibilities, authority, or even access to the various areas of the ship. It is the ideal role for players looking to simply take a break, and even has an alternate job title, Off-Duty, to denote characters with actual ranks and abilities who are simply taking the day off.
The rest of the role's alternative titles can be used to add flavor to any given Passenger character, and thus a hook with which to create role-playing opportunities with others. As this is the entire point of the role, taking advantage of this opportunity is highly recommended.