Jack is a friendly and enthusiastic front loader.
When Jack first started working, he was eager to work, and took on jobs that weren't for him, which got him into trouble. However, he learned from his mistakes, and was able to help stop a bridge Thomas was on from collapsing. Because of this, Miss Jenny allowed him to stay with The Pack.
Jack was like a toddler at first, who was still learning about the world and how to stay out of trouble. He is brave and will not take any hassle, as seen when he stood up to Max when the latter was bullying him and Alfie.
Jack is painted red with the top half of his cab and his wheels painted cream. He has the number 11 painted in white on his sides. From King of the Railway onwards, the top half of his cab is painted grey, his back wheels are painted grey and his front wheels are painted red.
- Season 2 - Races and Alfie's Lucky Day
- Season 3 - Jack and Alfie Swap
- Season 4 - Stories of Digging, Duck and the Coaches, Broken Down Crane, and George and Buster
- Season 5 - Nigel and Bumble Bucket
- Season 8 - Mucking Mud and A Treasury Christmas