Fergus knows the rulebook off by heart, and his catchphrase is "Do it right!" His insistence on doing everything absolutely according to the rules can annoy the other engines, but he is a decent engine at heart and will not hesitate to help others in trouble. Fergus has a slight but persistent cough which affects his speech, caused by working at the dusty cement works.
Fergus is based on the Aveling and Porter 2-2-0 'T9' class railway traction engine No. 9449 "Blue Circle", which is the only one left in the world
Fergus will appear in the series soon.