A Monster Surprise is a magazine story.
The Fat Controller's grandchildren are making a go-kart for a big race and the Fat Controller asks Percy to collect some wheels, wood and rope from Bert at the scrapyard. Percy is worried; he thinks the scrapyard is scary.
Percy tries not to look at all the broken trucks and coaches when he arrives at the scrapyard. Bert soon hurries over and asks if Percy is there to be scrapped. Percy tells him that he is there to collect the materials for the childrens' go-kart. Bert tells Percy to look in the shed. Percy goes into the shed and comes racing back out again. Percy tells Bert there is a monster in the shed, but Bert just laughs until his air vents ache. Bert explains that it's just a go-kart that some little girl has painted a scary face on. Percy feels very silly indeed.