Taro:

Taro is a converted Japanese electric loco who is usually in charge of the island's gas & oil deliveries, and running "The Blue Train." He is kind engine, although sometimes he doesn't quite understand the other engines due to his origins. However, he is hardworking and a good friend to all. He can get quite moody at times if he feels overworked, but the other engines all know that Taro is as good as any engine can get.
Taro originally had different couplings to the other engines, but has since been adapted to run with the other Sodor stock.

FACT: Taro was almost given an evil personality, but this was dropped for a more likeable character.

John And Adam (Truck):

These two trucks came to Sodor with Taro, and are his own two trucks. They are used for transporting oil and gas around Sodor.
John is constantly grumpy, wishing he could do more than deliver oil and gas, and sometimes wishes he could move of his own accord to see more of the railway.
Adam is usually quite upbeat and positive, hardly ever having something negative to say. However, he can be  quite gullible, which John and Diesel sometimes uses to their advantage.

FACT: These two trucks were originally set to have been on the island for years, but not usable due to their different couplings. It was decided this would be rather unrealistic, as those would have been changed in real life, so they were brought in with Taro to the railway.

The Blue Coaches:

Four carriages which form "The Blue Train", a night train with sleeping accommodation on board. They were brought over from Japan to give Taro another job to do, as, at the time, he had different couplings to the rest of the railway.
Chris is the guard and luggage carriage, and believes he is the most important coach of the train.
Asako is one of the sleeping coaches, and has a big heart. She rolls smoothly and enjoys seeing the world pass by.
Cian is another sleeping coach and usually sits behind Asako. He doesn't see much of the world and is rather quiet, but when he gets talking those around usually listen with interest.
Hana is the buffet coach of the train. Not only this, she can also be adapted to connect straight to Taro if Chris is not available for use. She is quite proud of this, but doesn't let it make her feel more or less important. Like the other coaches, she is quite friendly, albeit sometimes a little chatty.

FACT: The couplings for these coaches often dis-connect during filming, making them one of the more awkward trains to film with. The four coach train also takes a lot of space off-set to store, thus why they are rarely seen in the series.

Jeffery:

Jeffery is a small engine, and one with attitude. He would rather sleep than do work, and can be rather grumpy if he is disturbed. He does care about his friends, and especially his sister Rebecca, but does get on their nerves with his smug attitude. If there is something he doesn't like, he is not afraid to make it known and often speaks his mind.
When he does get working, Jeffery will ensure he finishes his job properly, as he fears he will be asked to do it again, meaning he can't go away and rest.

FACT: Original thoughts for his personality saw Jeffery being an overprotective brother, always following Rebecca about to make sure she didn't do anything silly. But this characteristic was dropped as a grumpy personality could be used in more storylines.

Rebecca:

Rebecca is a sweet little engine, and is Jeffery's brother. She likes spending time in the countryside as she likes the calm and quietness of it all. She is young, which sometimes affects her judgement, but usually manages things first time. She will always listen to the other engines if they have a problem, and knows that she can rely upon them for help too. Rebecca is also the only engine who can get Jeffery to do work without any bother.

FACT: Rebecca saw two personalities before her current self. Originally, she was to be the grumpy engine out of her and Jeffery, but this was quickly dropped. Her second persona was similar to her final one, but she fell in love with Percy and followed him everywhere. This was dropped, so that the series could remain as true to the Awdry series as possible.

Queen Elizabeth:

Queen Elizabeth, named after the Queen of England, is a visiting engine and is the same class of engine as Rebecca and Jeffery. She can think much of herself at times, but respects the other engines as she knows the true value of friendship.
She is quite vulnerable emotionally, and if something she is not used to confronts her, can feel isolated and frightened. But she does not let this stop her from doing her work, and will pull through in the end.

FACT: A face with a small crown above was going to be made for the character. This never happened as, at the time, it felt disrespectful toward the Queen, and it was thought it might upset Royalists to place a face on a model named after her majesty.

Ben:

Ben is another little engine, who works at the scrap yard shunting the trucks. He can be quite nervous at times, usually expecting the worst to happen, and panicking if it does. He often underestimates his abilities, and because of this usually surprises himself. Ben always works to do his jobs well, and right anything made wrong by Rhys.

FACT: It is not known exactly why the character was named Ben, when there was already a Ben on Sodor, but one contributing factor was the idea that it would be likely at some point that two engines with the same name would meet, like people would in real life.

Rhys:

Rhys is one steam engine that many of the Sodor engines wish hadn't been brought to the railway. He is extremely clumsy, often causing accidents, which take a lot of time to clear. He means well, but more often than not this results in something going wrong.
He is not the smartest engine, usually having trouble even talking properly, so ends up babbling instead.

FACT: Rhys came to Sodor at the same time as Ben by following him onto his ship. He only did this because Ben was his only friend and Rhys was scared of being alone.

Black:

Black is one of the larger engines on the railway. His proper name is County Of Gloucster, but prefers being called Black for reasons he has not yet made known. He is also one of the few big engines who doesn't seem himself as better than the little engines.
Black has a big heart and always helps where needed or wanted. He is strong and, when he wants to be, fast, but prefers a nice slow, calm run rather than a rushed and ruined one.

FACT: The model used for Black is the unluckiest model used for the series. Before the series began, a "slide bar" for one of the rods snapped off, meaning the rod had to be removed. The model then suffered problems with a split cog on the main driving wheel, which left the model jumping as it rolled along. These have now been sorted and repaired.

Adam (Tank Engine):

Adam is another clumsy engine, but he is nowhere as bad as Rhys. Where Adam differs significantly is in that he will learn from his mistakes, and try not to make the same one twice. Adam can sometimes feel jealous of the bigger engines and their strength and work, but he is usually happy with the jobs he is given.

FACT: Adam's model comes from the My First Hornby trainset, which was a Christmas present recieved by my brother.

Lord Of The Isles (LOTI):

LOTI a unique engine, and a very smart one at that. She was brought in at first to help with some Easter celebrations and has had her visit extended. Very elegant and polite, she is grateful for the fact she has not been scrapped, unlike many of her class. LOTI is usually found running the mainline trains with a set of smart GWR coaches.

FACT: LOTI was very rude to Black upon his arrival as she feared he would be competition for her job. However, after he had an accident trying to prove her remarks wrong, she has learnt her lesson and improved her attitude towards the others.

Gordon (Tank Engine):

A Southern railway tank engine who can sometimes ignore helpful advice of others. He spends most of his time working freight trains and shunting trucks, whom he dislikes greatly, as they do him. Gordon can sometimes act on initial thoughts which often lead him to trouble, but he always tries to put it right himself to prove he is capable of tough work.

FACT: The original idea was to introduce Gordon while the big express engine was away at the works, so that the railway always had a Gordon present. But the idea of having the two Gordons together causing confusion in the name was preferred over this.

Jack:

A high speed inter-city train who was brought in to give James a rest from express duties while Gordon was away for repairs. Jack is very friendly with the steam engines and enjoys gliding along the rails as he travels along. The passengers have never complained about Jack being rough or late, which he is quite proud of as not many engines have acheived this. His only fear is that he will be sent away from Sodor and never see his friends again.

FACT: Jack's model is like The Blue Train. It is quite long when in its full length, so is very rarely set up complete. Because of its age, the model also requires a few minutes running in to warm the motor up before filming with it can commence.

Sonic:

One of the shunting diesels on Sodor, who likes a race. Sonic is a very speedy engine, who dislikes going slow when avoidable. He oftens teases the other engines for being slower than him which can annoy them, and often talks too fast for the others to understand him. His need for speed can lead to trouble as he passes signals and points set against him.

FACT: Sonic came to Sodor with his brother on Halóween, and had a very scary experience that night. Since that night, Sonic spends every Halóween hiding in the sheds, scared to leave in case of any more spooky occurances.

Joseph:

Joseph is Sonic's twin brother, and is a complete contrast to him. He prefers to go slowly and take care over each job he is given. The other engines have found he is good company, and has proved himself very trustworthy. Joseph is almost identical to Sonic, the only difference being his paintwork, which was changed shortly after arrival so the two engines could be distinguished easilly from one another.

FACT: Joseph is easilly shaken by things, but the other engines always help him when they can. He can be especially bad around Halóween, just like Sonic.

Tom:

Tom is a small blue engine with his own branchline and rake of coaches. He has known Thomas for many years, as he used to work with him on another railway, so enjoys spending time in his company due to their freindship. Tom is a multi-tasker, often taking on several jobs in one go to prove his abilities, which he can cope with easilly.

FACT: Before coming to Sodor, Tom was on display in a museum. He disliked this because, although being operational, he was very rarely run on the demonstration track. For a short while, this caused problems for Tom's parts, but he was fully repaired when his branch line opened.

Fenchurch:

Fenchurch is named after the engine on the Bluebell Railway, and good friend to Stepney. He is also very brave, and able to push himself to the limit to help others or, on one occasion especially, stop escaping theives.

FACT: Fenchurch's model does not have any buffers of its own!

Normandy:

Another engine named after that on the Bluebell Railway, Normandy is Fenchuch's closest friend. He is also good friends with Stepney. Normandy arrived at first to help with the work at the docks and harbour, but now spends a lot of time travelling across Sodor with maintenance trains to check the track is good condition.

FACT: The model for Normandy only has two buffers of its own.

Charles Dickens:

Charles Dickens is like Taro, in the sense that he is a converted electric. He is often used for the larger and heaviest good trains on the railway.
Charles Dickens is a great storyteller, and the engines love to end their day listening to his tales.

FACT: Charles Dickens was supposed to have a face, but, because the model is owned by my brother and he requested it, this was dropped. One shot in the earliest version of Navigation does show Charles Dickens with a face.

Eddie:

Eddie is a small industrial locomotive who was brought to the island when the work on Sodor was too much for all the engines one summer. He single-handedly managed to sort the island out and got everything going again. He is a bit of coward though, and doesn't like to be challenged to something new. Eddie will always fight to get a place in the shed, as he doesn't like sleeping outdoors.

FACT: Eddie's model is one of the most temperamental models used in filming. The wheels pick up dirt easier than any of the others, so needs frequent cleaning before filming with Eddie can be completed.

Jonathon:

An shunting diesel who works with Ben and Rhys at the scrap yard. His first day, the scrap diesels nearly scrapped him, as they disliked his kindess to the steam engines. Thankfully, he was saved by Ben, and the two have become great friends. Jonathon likes to explore the island to try and find new things, and on one of these ventures discovered the carriage Wheezer.

FACT: Jonathon's rear coupling has a weight on the back inside the model, which often causes him to uncouple from trains during filming, especially if the truck has no coupling hook.

Benny:

Small but strong, Benny is a maintenance crane, often used on rail works. He enjoys the company of Beth, Toad and Rocky, and will spend much time talking to them about nothing in particular. He does sometimes feel shadowed by Rocky, but he knows that his work is just as important as Rocky's. Being small, Benny can also reach places that Rocky cannot.

FACT: Benny is actually stronger than he looks. He can't lift some of the big engines, but he can easilly lift Rocky onto the rails should he topple over or derail.

Beth:

Beth is Joseph's personal brake van. She can be quite controlling at times, but does a grand job in keeping the trucks in order. sHE is a good friend with Toad, and the two often share stories and tips on their ways to control trucks. Beth enjoys travelling with different engines, as being with Joseph can become repetitive after a while.

FACT: The character of Beth was actually introduced completely unintentionally. She appeared briefly in the original episode, and some viewers noticed her. Her character isn't seen often in the series, but her model often appears faceless at the end of trains or in sidings.

Wheezer:

An old coach who was, for many years, abandoned in some sidings at the back of the scrap yard. He was found by Jonathon and, after a rough start, rejoined the Sodor carriage fleet as another useful coach on the branch lines. Being so old, he has many tales to tell, and sometimes fears he will be left behind again one day. However, he has become popular with passengers, so it is unlikely this will ever happen.

FACT: Wheezer's model appeared in the series several times before being introduced under this character.