As the episode begins, we find Baby at his house wearing a colorful spotted birthday hat sitting on a blue mat with a colorful spotted birthday present. The house is all decorated with balloons and a streamer on the wall. The Narrator welcomes the viewers and tells them that today is Sophie's birthday. He allows the viewers to say hello to Baby. Then, the doorbell rings. It is Sophie who has arrived for her party. She is wearing her normal clothes with a pink ballerina skirt covering her diaper. Baby and Sophie hug. The Narrator allows the viewers to say hello to Sophie. Butterfly arrives and gives Sophie a pink birthday tiara. The Narrator thanks Butterfly and suggests they play a birthday game before Sophie opens Baby's present to her. Baby and Sophie agree and follow Butterfly to where pin the tail on the donkey is set up. The Narrator reveals that they want to play that game and invites the viewers to help them. He gives Sophie the tail for the donkey and tell sher to pin the tail on the donkey.Sophie looks around and puts it on Baby's nose. The Narrator says that's where Sophie thinks it goes and asks the viewers if that's where it goes. He then reveals that's not where it goes. He then asks the viewers to help Sophie figure out where it goes. She takes the tail off Baby's nose and puts it on the donkey's bottom where it goes. The Narrator comments saying that's very good. Butterfly arrives again and the Narrator tells the viewers that she has a surprise for them. They follow her to a striped mat where a birthday cupcake is for Sophie. The Narrator tells her to make a wish and blow out the candle. She tries to blow out the candle but fails. The Narrator invites the viewers to help blow out the candle. Baby also helps. They all blow out the candle together. Baby and Sophie eat the cupcake and get their faces messy, The Narrator cleans their faces and puts Sophie's present down so she can open it. She opens the present to find a jack-in-the-box. Baby and Sophie attempt to turn the handle but fail. The viuewers are invites to help. They do it correctly then. As they turn the handle, the tune to "Pop Goes The Weasel!" plays and a clown pops out. Baby and Sophie are very happy. The Narrator closes it again and says they want to play again. They do it again and are still very happy. Then the Go Baby! music plays. The Narrator asks if they hear the music and reveals it's time for the Go Baby! dance. Baby and Sophie dance and a clown and a rocking horse dance too. The Narrator comments saying this is a wonderful party and thanks the viewers for helping. He allows the viewers to say goodbye to Baby and Sophie. The episode then ends.
- Place: Baby's house
- Theme: Sophie's Birthday party
- Characters Present: Baby, Sophie, Narrator, and Butterfly
- Airdate: November 14, 2006 (last year as the 50 minute premiere movie Bob the Builder: When Bob Became a Builder on PBS Kids at 7:00 PM Eastern) (series finale)
- This is the last episode of the series.
- This is also the last apperance of Baby, Sophie, Narrator, and Butterfly.
- This is also the last episode to air in 2006.