Bill and Ben are tank engine twins belonging to the Sodor China Clay Company. They are young and cheeky and love playing jokes on the bigger engines, but are kept in order by Edward and BoCo. They work in the china clay works and at Brendam Docks, where they are kept busy shunting trucks.
The Railway Series
One day, Bill and Ben returned from shunting some trucks to find that some other trucks they had shunted earlier were missing. Their drivers, after examining a puddle of oil on the ground, concluded a diesel was responsible. After the twins argued over who brought the "diseasel" into the yard, the drivers suggested they go looking for the diesel. The twins were horrified at the possibility that the "diseasel" might magic them away like he did with the trucks, but their drivers quickly persuaded them otherwise, and so they set off.
At last, the twins found the "diseasel". While Ben ran behind, Bill confronted the "diseasel" over the theft. The "diseasel" claimed the trucks were his and ordered Bill to "go away"; Bill pretended to be frightened and slunk away, remarking, "You'll be sorry". With that, Ben ran up and accused the "diseasel" of being a "truck stealer", before running back so Bill could run up again. This continued until the "diseasel", under the impression that there was only one very swift and annoying saddletank, became so giddy that his eyes "nearly popped out", just as the twins puffed up beside him. The "diseasel", initially confused, laughed at his ignorance. When Edward arrived moments later, inquiring as to why Bill and Ben were not shunting, the twins angrily claimed that the "diseasel" had sneaked into their yard and stolen their trucks. Edward soon realised what was going on and explained the situation. The twins, embarrassed, apologised to the "diseasel", who asked to be called BoCo, and then left to shunt some more trucks, leaving Edward and BoCo to laugh about the incident.
A few days later, after BoCo took the Express in James' absence, Edward recounted what Gordon had said about branch lines to the twins. The next morning, after Gordon ended up at Brendam after a series of events involving poor preparations and a large floppy green hat, the twins sneaked up beside him and loudly recounted what Gordon had said about branch lines. Concluding that the engine beside them could not be Gordon, the two declared he was nothing more than a pile of old scrap-iron, and began to contemplate what they should do (Bill was all for sending Gordon to be scrapped, while Ben favoured the more humane option of dumping him in the sea), all the while ignoring Gordon's protests, until at last, BoCo arrived. Gordon begged him to save him, and so BoCo threatened the twins to leave with the trucks he had brought. The twins quickly left, leaving Gordon with BoCo. BoCo wisely neglected to tell Gordon the twins were joking.
In 1988, Thomas was sent to work on Edward's Branch Line while repairs were carried out on the bridge. The twins were quick to tease him about his colour, but Edward was savvy enough to send the twins away before an argument broke out.
After Thomas returned to the Yard, covered in dairy from a collision with a farm lorry, the two teased him even more about his new livery. This continued until Edward announced a party of enthusiasts were coming, and threatened that he would not bring them to see the twins. The twins, excited, decided instead to worry about their own paint - for example, how clean it was - although one day, when the drivers remarked that "the enthusiasts would not eat their dinner off them", Bill quipped that "They might if we were Thomas".
When at last, the enthusiasts did arrive, a photographer with an "instant" camera began harassing Ben by continuously taking pictures of him, even after the remainder of the crowd went to watch Bill tug a boat into deeper waters. At last, the photographer prepared to take one final picture, just as Bill's driver arrived to ask for assistance. Ben's driver turned on the steam just as the photographer took the picture; disgusted with the poor quality of the shot, he abandoned it on the floor and left. The picture was later discovered by Bill's driver after the two rescued the boat.
The repairs to the bridge took a long time, and Thomas was still at Brendam when the rainy season came. At the "Drain", a hollow in the land where rainwater collected, the water even began to come near the rails, although no one took much notice. One particularly wet day, as Ben returned from the Workings, the wind whipped the rainwater into a wave which swamped Ben, dousing his fire. His fireman went for assistance, and brought Thomas to help. While Thomas dragged Ben out, Bill took away the trucks. When at last the water subsided four days later and Bill returned to Brendam, the two made a pact to never tease Thomas again.
Thomas & Friends
Bill and Ben make their first appearance listening to Percy recount the time he got caught in a flood helping Thomas, before being shooed off by Henry, as they were in a shed specifically for the Fat Controller's engines.
One day, Bill and Ben were sent to work in the yard. They got to use the turntable as a reward for their hard work. But Bill and Ben were accidentally sent down the same track and they ended up buffer-to-buffer. They each blamed each other for the incident and refused to speak to one another. At last, Edward and BoCo lost patience and the Fat Controller heard about the incident. He gave the twins a chance to work together, and sure enough, the plan worked. The twins started to speak to each other again. Bill and Ben sometimes find it dull up at the clay works and they wanted something exciting to happen. They got their wish when a rockslide devastated the quarry. Luckily, Bill and Ben had taken all of the workmen and the foreman out of the quarry before the rockslide. The Fat Controller was so pleased that he called them heroes.
Later, BoCo could not handle the twins as much as he used to, so Sir Topham Hatt had to bring in another diesel, Derek. Bill and Ben had heard from Percy that Derek had a toothache. But they soon found out that Derek really had teething troubles. The twins and Derek had to pull a train the next day, and Derek soon overheated. Together, the twins got the train to their destination. That night, they, BoCo, and Duck talked about Derek all night long.
When Salty was sent to work with the twins and Mavis with an important job, he impressed the twins with his skills for handling the trucks. When Salty handled the trucks with songs and tales of the sea, Bill and Ben became jealous. They became even crosser when Salty told them stories. Luckily for them, Salty was transferred to Brendam Docks. Bill and Ben met Salty again when they themselves went to the docks and started teasing Cranky. This time, they encourage Salty to tell them his stories, knowing that Cranky can't stand them. The twins spent the entire night being engrossed in and fascinated by Salty's many tales, and when they left the following morning, Cranky was pleased. Afterwards, Ben had to get new buffers, so he was sent to the Works. Bill became jealous and his mind drifted away from his work. After some trucks teased him, Bill crashed into a ditch. Ben arrived to rescue Bill and Bill was taken to the Works to be mended.
Some time later, Fergus was sent to help the twins at the quarry. They got tired of his "do it right" attitude. Bill and Ben collected a rock crusher from the docks and caused a rockslide. Fergus pushed them out of the way, but the twins returned the favour when they helped him out of the rocks.
Bill and Ben are Sodor's mischievous saddle tank engine twins, who have great fun in teasing the other engines of the railway. Each has four wheels, a tiny chimney and dome, and a small squat cab. They often work in the China Clay pits and quarries. Their loads of clay can be used for many things such as paper, paint, and pottery. They take trucks for engines on the main line and ships in the harbour and are regularly seen around Brendam Docks. They enjoy attention and love taking visitors and being photographed. They tend to work together, like most twins, but even this youthful pair can have their arguments among themselves and can squabble with one another. They are highly prone to playing tricks and being cheeky. They have even teased Gordon on more than one occasion. Duck has called them "the bees" before, for being terrors when they start buzzing around. Edward and BoCo are the only engines who can really keep them in order enough to put a stop to their games and make them scamper along and behave. There is no real harm to them, but even Edward admits that they are maddening at times.
Despite their cheeky and mischievous antics, if a dangerous event occurs, such as a rockslide, they are shown to be quick-witted and capable to act to rescue anyone in trouble.
Bill and Ben are based on the Bagnall 0-4-0STs "Alfred" and "Judy" of Par, Cornwall, who are both preserved and in working order at the Bodmin and Wenford Railway.
Alfred and Judy are painted in a green coat of paint, with yellow lining, although the former was once repainted in a yellow coat of paint, very similar to Bill and Ben's yellow coats of paint.
According to the foreword of Thomas and the Twins, Alfred and Judy are both Bill and Ben's twins.
In the Railway Series, Bill and Ben are painted dark orange with red lining. In the television series, they are painted dark yellow with red lining.
In the television series, Bill and Ben both have brass nameplates with yellow writing, "SCC" written on both sides in yellow and "Brendam Bay" on the front of their saddle tanks. In the Railway Series, they have number plates reading 1 and 2 respectively above both the back of their cabs and their faces. In The Diseasel, they have nameplates, but from Wrong Road onward, they have their names painted on their saddle tanks.
- A behind the scenes picture reveals that Bill and Ben were to have numbers on their smokeboxes above their faces.