Cormac is very cheeky chugger who enjoys pulling small practical jokes on the chuggers but he never takes his jokes too far and always tells the chugger if he has played a practical joke as well. He is very supportive and always works hard to complete his work, even if he has to take a break very often.
In his first appearance, he helped Brewster take the last section of the Tootington Tunnel to the worksite. The load was very wide so they had to use two flatbeds and work side by side. However, Cormac got tired and as they went round a bend, then tunnel section fell off and rolled down the hill. Brewster and Cormac had to chase it and then catch it just at the right moment. Then they happily took the tunnel section to the worksite and the tunnel was complete. He was present during the Iron Chuggers contest and set up the wagons with the weight that Speedy and Zack wanted.
Cormac is of a freelance design. Therefore, he is not based on any specific prototype.
Cormac is viridian with some thick yellow stripes. His bottom jaw, buffer beams and cab roof is yellow too and he has an orange siren light.
- He can carry heavy rocks and crates.
- He carried a prank for Brewster and Old Puffer Pete.
- Cormac is able to spilt in two and spin around in order to load his other half himself.
- In German, he is called "Konrad”.
- In Chug Patrol, Out of Control, Cormac shouts “Hi Mum!” when he sees that he’s on Chug Command. While this could imply the presence of parents, this is more than likely a joke.
- In Cormac Patrol, Cormac reveals quite a few things: he's never been a hero, he's really good with rolling stock and machinery, and he hates having nothing to do.
- Cormac's back end can rotate, as shown in Tour Guide Harrison.
- He is the fourth chugger who is able to rotate 360 degrees. The first is Zephie, and the second and third are Hoot and Toot, respectively.
- Cormac has the distinction of being the only chugger with no confirmed real-life counterpart.
- Season 4 - The Tootington Tunnel and Iron Chuggers
- Season 5 - Cormac Patrol, Trainee Camp, Tour Guide Harrison, Delivery Challenge, Skipper Stu and the Steam Crane and Fletch Shines
- Season 6 - Chug Patrol, Out of Control, Wilson's Wag-A-Lagon, The Fast, The Strong & The Wilson (does not speak), Chuggington Noir, Tai Tracks (cameo), Chugging Home for the Holidays (cameo), The Royal Chugger (cameo) and Celebrate Chuggington (cameo)
- Roundhouse Song (cameo)