Special Surprise is a magazine story. It was republished in 2016 as The Perfect Party.
When Thomas and Percy pull into Knapford, the Fat Controller is waiting with special jobs for them. A new family is moving to the island and Thomas is to collect them and take them to their new home. The Fat Controller tells Percy that he is to collect a doctor to take to a poorly boy.
That night, the engines talk about their special jobs. Thomas says that the new family have a boy who has a birthday coming up and he wants to do something special. Percy says that the poorly boy he visited missed his birthday because he was so poorly, but the doctor says he's doing much better now. After a good night's sleep, Thomas and Percy decide to throw a party for the two boys, but they cannot decide what sort of party to have or where to have it. The two engines go about their work, but they cannot stop thinking about the party.
As Thomas pulls into the last station on his branchline and the passengers disembark, Thomas spots a familiar face; it's Mr. Bubbles the clown. Thomas tells Mr. Bubbles about the party problem and the clown generously gives Thomas' driver lots of spare balloons for a balloon party.
Thomas races off to tell Percy that the party can be a balloon party. Percy is still worried as he cannot find anywhere to have the party; the Town Hall is being used and Knapford station is too busy.
Later that day, Thomas and Percy pick up the two boys. Both boys were amazed when they saw balloons everywhere. Thomas tells them to climb aboard as they are about to go on a balloon party all around Sodor. The two boys climb into Thomas and Percy's cabs and declare that it is the best surprise ever. Thomas and Percy had made two little boys extremely happy.