Bill and Ben are a pair of twins, who work at Brendam Docks on the Island of Sodor. This is located at the end of Edward's branchline, and both engines are nearly identical. Both of them are painted yellow, and are saddle tank locomotives. They both have four wheels, squat chimneys and domes, low, squat saddle tanks, and small cabs. The reason for these squat features is the fact they were built for a railway in Devon which had limited height clearances, and as a result they needed to be small in order to fit under the bridges and through the tunnels which characterised their branchline. However, it had closed in the 1950s, and both of them had been purchased by the Sodor China Clay Company for their own line, running from their quarry at Brendam Clay Pits down to Brendam docks, where the china clay is offloaded from the trucks and onto waiting ships to go all around the world (alongside racing cars, tank engines, and men in black suits and top hats hitchiking their way around the world).
They have drivers, naturally enough. Bill is driven by a young girl with brown skin and red hair, matched by a pair of glowing green eyes. She has freckles on her cheeks, and typically wears a two tone brown long sleeved shirt, a pair of green slacks, and red trainers paired with white socks. Her name is Barbara Seldon, a name she absolutely hates with a passion, so most people call her Babs Seed. Ben, on the other hand, is driven by a girl with yellow hair and light pink skin. She typically wears a red and black striped shirt with a black skirt and red boots. Her name is Samantha Seldon, and she is Babs' older sister. Like Babs, she is usually referred to by her nickname of Sunflower Seed.
The work that Bill, Ben, and their drivers do is crucial for many industries. The china clay is needed for pottery, paint, and many other things. A typical day of work consists of them pulling loaded trucks to the harbour, and taking the empties back to be filled. They then take the full trucks to the harbour, and return the new empties. This pattern continues throughout the day until the work is done.
One day, the twins left some trucks next to the cranes to be unloaded, and took some empty trucks back with them. When they dropped these ones off at the harbour later that day, they were horrified to see that they were all gone! In their place were two pools of mysterious black liquid.
"Where have our trucks gone?" Bill asked, very surprised.
"They've vanished!" Ben replied. "Somebody's taken them!"
"Thanks for stating the obvious!" Bill snapped back. Babs got out of Bill's cab and bent down to smell the patch of black liquid.
"Hmm," she said, in her thick Bronx accent. "That's hydraulic fluid. Somethin's gone and taken the trucks, and it's probably a diesel."
"Jeepers!" Sunflower replied, in an equally thick accent. "That sounds bad."
"A what'll?" asked Bill, very confused.
"A dieseasel," Ben replied. "Remember, there's a notice about them in the shed. 'Coughs and sneezles spread diseasels'."
"Ah," Bill answered.
"You had a cough in your smokebox only a few days ago," Ben said, with a mean smile. "And then this diseasel had gone and stolen the trucks. It;s your fault these trucks are missing!"
"It isn't!"
"It is!"
"It isn't!"
"It is!"
"Stop arguin' guys!" Babs shouted. "Look, this diesel has gone and taken our trucks. We need ta go and get them back before it takes them further!"
Ben gasped. "But the dieseasel will magic us away like he did the trucks!"
"He won't magic us," Sunflower laughed. "We'll magic him. You two, to most observers, look exactly the same. So we'll remove your nameplates, shut the cab windows, and boy will that diesel get a nasty surprise!"
And that is exactly what they did. Both engines left the yard and puffed out onto the mainline, but with their small wheels, it took a while.
"It's in the yard at Wellsworth?" Babs asked, frustrated. "That's 20 miles away or somethin'!"
"If it was that far," Bill replied, "we'd have run out of coal and water!"
After a very long journey, they saw their trucks parked in a siding, ready to be moved onto the mainline. At the front of the train, something was revving. Ben stopped at the yard threshold, but Bill rolled forward, up the side of the siding. The tension mounted as dramatic piano music played in the background, before Bill rolled level with the diesel. He was very long indeed, painted dark green, and with the British Railways early crest on his side. He had six wheels on one bogie, and four wheels on the other. He had the number D5705 painted on his cabside, and he looked very cross. He looked at Bill grumpily. "Do you mind?" he snapped. "I'm trying to rest here."
Bill looked at him, Babs being very careful not to make a sound. "I'd like my trucks please," the tank engine said.
"These trucks are mine," the diesel replied. "I'm taking them to the yards at Knapford to be marshalled into a train going to Bridlington Goods Yard. Now go away."
"They say it's the hottest place in town!" exclaimed a voice, and the cab door swung open. Sat there was a man with greyish brown skin and black hair, with blue eyes to match. He wore a formal suit with a red tie that had a doller symbol on it. Otherwise, his attire was fairly typical for a train driver of the 1950s. "Anyways, you can't have these trucks. They're going to the mainland and that is final."
Bill pretended to be frightened. "You're a big bully, both of you!" he whimpered. "You'll be sorry!" and he sped away before the diesel could say anything.
And then the plan went into action. Ben flew forward on the other side, and whistled loudly. "Truck stealer!" he shouted, before shooting back into the yard.
Bill shot up the other side, and stopped moments later, whistling again, and then he went back. Ben then came forward again, and then retreated, his eyes spinning round and round as he did so.
This went on and on until the diesel's eyes nearly popped out. "STOP!" he cried. "YOU'RE MAKING ME AND MY DRIVER DIZZY!"
"I'm so Dizzy, my head is spinnin'!" Babs sang loudly, as she through open the cab door. Bill and Ben came to a stop on opposite sides of the diesel.
The diesel looked at Ben, then at Bill, and back to Ben again. "So, there are two of you?" he asked.
"Yes," Ben smiled. "We're twins."
The diesel laughed. "I might have known it."
Just then, Edward rolled to a stop. "Bill and Ben?" he asked in confusion. "What are you two doing here?"
"Yeah," Applejack added. "Ain't ya both supposed ta be shuntin' trucks in the harbour? Trucks Eddie and Ah are meant ta be takin' ta Tidmouth right now?"
"We're not playing!" Bill protested.
"That's right," Ben said. "We're rescuing our trucks from this diseasel, who took them without asking. Even you don't take our trucks without asking."
"But it's not the diesesel's fault," said Bill. "It's Ben's fault!"
"What?" Ben exclaimed. "MY FAULT?"
"You were the first to start talking about this dieseasel! It's your fault!"
"Is not!"
"Is too!"
"IS NOT!"
"IS TOO!"
"Enough!" Edward shouted. "There's no need to be rude. Why, this engine is a Metropolitan Vickers English Electric Type 2!"
"Or Class 28," said the diesel's driver.
Bill, Ben, Babs and Sunflower all looked very sorry. "Sorry," they mumbled.
"It's alright," the diesel replied. "I didn't understand about the arrangements, and neither did my driver. You can call me BoCo."
"But yer CoBo," Sunflower said, confused.
Applejack looked sternly. "Ah'm appalled that mah own cousins would act in this way. You four can make it up ta BoCo by collectin' his trucks fer him, and then takin' these ones back. And don't forget about the trucks for Eddie and me!"
As the two tank engines shuffled off, the driver glanced over to Applejack. "Hey, you're of the Apple family in Arlesburgh, right?" he asked.
"Er, yeah?" Applejack replied.
"Why, it's a pleasure to meet you!" he answered. "Name's Ford Roberts, but I'm usually called Filthy Rich, or just Rich."
"Those four meant no harm," Edward said, with a smile. "But they can be maddening!"
"Maddening is the word!" BoCo laughed.