Bill and Ben are tank engine twins.
- Season 1 - Where's BoCo?, Repairing Old Slow Coach (cameo), Mavis Strikes Out (mentioned), and The Funny Trick
- Season 2 - Mavis and the Track Repairs, Off to the Works, The Crashing Kipper, Golden Engines, Tender Engines Don't Shunt! (mentioned), Derek Comes Home, and Sidney's First Christmas (cameo)
- Season 3 - Thomas and the Twins, Stealing Trains, and Frozen Points
- Season 4 - Finally at Home!, A Blue Mountain Disaster! and Rusty's Rough Morning (Ben only)
- Season 5 - Gordon Gets Crushed (cameo), Be On Your Guard!, Kelly's New Friend, Thomas Gets Juiced, and "It's A Great Story After All....."
- Season 6 - The Faulty Sheds (Bill, Ben does not speak), The Wrong Sort of Coal (do not speak), Triple Trouble