Bob's First Build is the 4th episode of the twenty-first season. It was written by Steven Darancette.
Muck feels terrible when he accidentally collapses Bob's old shed. To make him feel better, while Bob is away getting braces for the rebuild, Scoop recalls how he first met Bob and helped him build it - and the mistakes that the young Bob made along the way. Includes an appearance by Bob's father
- According to a YouTuber called James A Williams, he stated that this episode is the same as When Bob Became a Builder.
- Jimmy Hibbert Voices Bob's Dad While David Holt Voices Young Bob.