Percy, Wilbert & Diesel is a Potential Plotlines episode.
Percy and Wilbert warn Diesel about a broken bridge. But Diesel ignores their advice and moves to collect some coaches. Percy and Wilbert tell Duck that Diesel is a devious diesel engine. At Knapford, Diesel buffers up to the coaches and oils away. Suddenly, Diesel sees the broken bridge and crashes into the barrier. He dangles over the edge of the broken bridge. Percy and Wilbert tell Thomas about Diesel's accident, and Wilbert races to Diesel's rescue and pulls Diesel back to the rails. After Sir Topham Hatt brings Diesel back to the Smelters, Diesel feels silly.
- Stanley (cameo)
- Oliver (cameo)
- Sir Topham Hatt