Mighty Mac is a blue double-ended Fairlie duplex locomotive. Mighty is the "older" of the two and is distinguished by a small flick of hair. Mac is the "younger" half and is distinguished by his youthful features, round nose, and freckled cheeks.
Despite the opposing personalities of the two ends, they are technically one engine.
Prior to their adoption into the Skarloey Railway family, Mighty Mac had only worked in the shunting yards. Their lack of knowledge beyond their boundaries created much conflict between the two halves (for example, which end is in charge of doing what), which placed themselves and their passengers in great danger whilst running an important errand. But, with advice from Thomas in mind, they were able to complete their task and realise the value of working as one.
Mighty Mac is based on a Double Fairlie locomotive of the Ffestiniog Railway with added bufferbeams. A Double Fairlie locomotive from the same railway appeared in the 1979 Annual.
Mighty Mac is painted royal blue with yellow and red lining. On Mighty's side, his cab windows and tank caps are lined with yellow, while on Mac's side, they're lined with red.
- Season 9 - Mighty Mac, Tuneful Toots (cameo), Rheneas and the Dinosaur (cameo), The Magic Lamp (cameo), Duncan and the Old Mine (cameo) and Skarloey the Brave (cameo)
- Season 10 - A Smooth Ride (do not speak), Duncan Drops a Clanger, Thomas' Tricky Tree (do not speak), Which Way Now? (cameo), Duncan's Bluff (cameo) and Missing Trucks (do not speak)
- Season 11 - Sir Handel in Charge, Cool Truckings (cameo), Ding-a-Ling and Wash Behind Your Buffers (cameo)
- Season 12 - Mountain Marvel and The Party Surprise (cameo)
- 2006 - Pull Together
- 2008 - Smokescreen
- 2010 - Going First
- Taketoshi Kawano (Japan)
They play two of the llamas in Raymanladdin (ThomasTenCents34526's Style)
- They are two of the llamas in The Prince Ali parade.
They play Napoleon and Lafayette in The Aristotoys (ThomasTenCents34526's Style)
- They are two dog buddies.
- Unlike most double fairlies, Mighty Mac has a whistle at both ends of their model.
- Mighty is the only engine to have what appears to be hair.
- In Season 11, their whistles were changed to Harvey's at a high pitch.
- Wooden Railway (normal and cancelled Talking Railway Series version; discontinued)
- Take Along (discontinued)
- Take-n-Play (discontinued)
- Motor Road and Rail (discontinued)
- TrackMaster (discontinued)
- My Thomas Story Library (discontinued)
- Wind-up (normal and metallic; Japan only)