Each Sim is given between 0 and 10 points for each of the personality traits below that dictates how they react to and with other Sims as well as how they act alone. Sims with 0 neat points, for example, tend to leak water everywhere when they take a shower. Sims with 10 active points will run pretty much everywhere. Sims that have 9 playful points or more will not be able to meditate, etc.
Slob - Neat
Shy - Outgoing
Lazy - Active
Serious - Playful
Grouchy - Nice
They also need to be assigned two turn-ons and one turn-off from the following list:
Fitness, fatness, stink, formal wear, underwear, swimwear, cologne, glasses, makeup, costume makeup, black hair, brown hair, blonde hair, red hair, custom hair, grey hair, vampires (Bon Voyage-specific options): Jewelry, Hard Worker, Unemployed, Logical, Charismatic, Great Cook, Mechanical, Creative, Athletic, Good at Cleaning, Zombiism, Robots, Plantsimism, Lycanthropy
The final thing that needs to be decided (and one of the most important) is their Aspiration. Their Aspiration will decide what kind of wants they'll have and how they'll get along with other Sims with similar or dissimilar Aspirations.
The options are:
Pleasure (this basically prompts them to do small little fun things like play games and take long bubble baths)
Family (this motivates them to start a family and/or interact intensively with the family they have)
Romance (they want to "woohoo" . . . all the time and with as many Sims as possible)
Fortune (they want the moolah and they want it now)
Knowledge (they want to know everything)
Popularity (they want to know everyone and not hate a soul)
Grilled Cheese (they want to talk, eat, sleep and breathe grilled cheese sandwiches. Nothing else.)
With that being said, allow me to put forth my thoughts:
Knowledge: Robin and Chopper
Popularity: Usopp and Zoro
Zoro and Luffy gave me the most trouble, but I decided that Zoro would be Ppoularity due to his desire to have the world know his name, even if he doesn't care if it's in a good or bad way. Luffy seems so carefree that Pleasure seemed a natural choice for him, and Franky's devotion to the Franky Family back in Water Seven prompted the Family aspiration for him.
Would anyone care to post their thoughts?