The inhabitants of Wheelie World have all been asleep for years thanks to a spell by the evil witch Fenella. But suddenly an egg appears in Wheelie World and when it hatches, a happiness dragon emerges that will break the evil spell.

The Wheelies are in trouble, their wheels and tires are wearing out and they have no replacements as Fenella the witch has cursed the plants in the spare parts orchard. Can Chorlton lift the curse and save his wheeled friends?

Seeing that Chorlton has gone picking flowers, Fenella plants a trail of beautiful flowers to lure the dragon to Spout Hall. She plans to capture him there. The Wheelies organise a search party but they needn't worry about him.

Fenella summons an Octoblob to lure Zoomer to a disguised Spout Hall. She plans to take the speedy Wheelie prisoner so that she can exchange him for Chorlton. But does the witch really want a happiness dragon in her home?

Fenella seems to have come up with a foolproof plan to get rid of Chorlton once and for all - frame him for a crime. So she steals King Otto's crown and magically leaves a trail of dragon-sized footprints - but she makes a mistake.

Everyone in Wheelie World is spring cleaning - except Chorlton. The happiness dragon has no wheels, so has no springs to clean. The Wheelies give him a Wheelie Cart to travel around on - much to the annoyance of Fenella the witch.