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.
- It is currently unknown when Mighty Mac will appear.
- Mighty Mac has no allocated voice actor as of now.
- 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.