Kelly was one of the first members of the Pack that Jack met, and he and Isobella both advised him to see the Foreman. A while later, he attempted to try and help Jack hold up a bridge that was collapsing, but by the time he had rushed over to the bridge, it had already collapsed.
Later, he told the story of the one-eyed truck to Percy and the rest of the Pack. He also gained a fear of strong winds after an accident in which he was blown over, but he got over this fear after he rescued Isobella from falling over. He later helped with the restoration of Great Waterton.
Kelly is good at heart and gets along with everyone. He is good friends with Isobella. He is seen by many as the team's leader, and is usually given the most dangerous work to do. He will not be rushed and understands that work of this kind takes extreme care. Kelly used to have a slight fear of strong winds, but he conquered that fear when he rescued Isobella.
Kelly is based on a Coles Vintage 1937 EMA 5 Austin K6 lorry.
Kelly is painted navy blue with a cream crane arm and red lining. His wheels are navy blue with red lining. He has the number 17 painted on his sides in white.
- Season 6 - Jack Jumps In and A Friend in Need
- Jack and the Construction Company - A Visit from Thomas, Jack Owns Up, On Site with Thomas, Percy's Scary Tale, Kelly's Windy Day, A Happy Day for Percy, A Tale for Thomas, Thomas and the Moles (does not speak), and Alfie Has Kittens
- The Great Discovery (music video cameo)
Kelly also appeared in two ninth season music videos.
- Kōzō Shioya (Japan; sixth season only)
- Kelly is one of the machines whose silhouette is pictured on the Pack's logo.
- Kelly has the same horn sound as Madge.