There is this poem I knew when I was little something about Belinda who had a dragon called Custard something to do with Mustard and a weelbarrow What was it?

The poem you're thinking of is "The Tale of Custard the Dragon" by Ogden Nash. It tells the story of a cowardly dragon named Custard who belongs to a girl named Belinda. Belinda's other pets, including a dog named Mustard and a cat named Ink, are brave, while Custard is often mocked for his timidity. The poem highlights themes of courage and the unexpected heroism of Custard when danger arises.