Slip Coaches are Great Western bogie coaches, which can be uncoupled at stations without the engine stopping.
Duck has three slip coaches, two male coaches and one female coach. It is currently unknown whether or not the coaches have any proper names, but Duck has given them the collective nickname of "Slippies".
Before coming to Sodor, Duck used to pull three slip coaches on "The Sunshine Line", part of the Great Western Railway.
Later, Duck told the other engines about his coaches. When the Fat Controller was concerned about passengers getting to their destinations on time during the peak summer months; James told him about slip coaches, claiming Duck's idea as his own. The Fat Controller purchased some slip coaches, and rewarded James with the chance to pull the coaches on Duck's Branch Line, but not knowing the red engine did not know how to time the uncoupling correctly. At Bluff's Cove, after uncoupling the rear coach, he slowed down to show off his paintwork. Because the last coach was still moving, it bumped into the back of the rest of the train. The slip coaches then refused to move, as James didn't know how to use them.
By coincidence, the slip coaches that the Fat Controller purchased were the same slip coaches Duck used to pull on the Great Western Railway and they were glad to see their old engine. Since Duck knew how to handle the slip coaches, he took over pulling the slip coaches from James for the rest of the day.
At Christmas, when Connor needed extra coaches for his last train on Christmas Eve, the slip coaches offered to help. The third was released at Kellsthorpe Road, the second coach was released at Maron, and the first coach was released at Wellsworth. Unfortunately, the first coach overshot the platform, but Thomas managed to shunt the coach to the platform.
The Slip Coaches are now permanently used on the Little Western, pulled by Duck. However, one day when Dowager Hatt was running the railway, the coaches were seen being pulled by 'Arry.
The Slip Coaches are very good friends with Duck. Like most coaches, they do not like being bumped by an engine. They can be very judgemental if they are not treated right, and need to be handled delicately.
The Slip Coaches are based on the Great Western Railway's Slip Coaches. These coaches had the unique ability in which they could be uncoupled at stations without stopping. The uncoupled coaches are stopped when the guard sets a handbrake.
The Slip Coaches are painted maroon and cream.
- Unlike real slip coaches, their slip couplings, slip levers, and guard compartments are located at the rear instead of the front.
- Duck's first and third slip coaches are the first male coaches to be introduced in the television series.