Carnival Costume is a magazine story.
George is boasting because he is leading the carnival procession. He tells Thomas that silly steamies cannot be in the prosession because engines cannot run on the roads. This gives Thomas an idea. He takes Lady Hatt to the school where, with the help of the schoolchildren, they help Thomas with his idea. George is surprised when he sees a Thomas in the procession - the schoolchildren were wearing a a big Thomas costume!
- The horrid lorry's number plate is blank.
- George calls Thomas a "silly steamy", but George is a steamroller.