This story is an homage to Harold and the Purple Crayon, updated and a bit more sophisticated, plot-wise, for slightly older (lower elementary) readers.
Henry's bedroom door is painted with blackboard paint, the kind you can write on in chalk and erase. Over time, it wears thin. He makes sketches in his sketchbook, and he and his best friend, Oscar, pretend play from them.
School sends home a note, asking Henry to curb his imagination and draw "true" bunnies eating lettuce or other veg for a National Vegetable Week art display in the cafeteria. He draws a ferocious dragon on his door instead.
The night before he's supposed to go to school and draw "true" bunnies, he has a dream. His door is black, a limitless black, the black of outer space and endless possibilities, making his door a portal to a new world, an adventure. Something breathes on his cheek.
When he wakes, the door is still ominous and blank. When he goes down to breakfast, he sees his toy robot on the stairs. Only it morphs into the chalk dragon, and he confronts it with his cardboard tube sword.
It flees into his room and inhales many of Henry's sketches. Henry needs his backpack to take to school, where you just know the dragon's dying to go and wreak havoc on that bunny veggie art display. It morphs into a rhino, then an octopus, and finally, when Henry thinks he's got it safely stuffed behind the bedroom door, it scuttles under the crack and heads down the stairs, while Henry's left to explain to his mother what happened.
On the bus ride to school, the bullies make fun of his artwork, and the bus driver proves to be a very philosophical sort -- urging Henry to let his artwork free into the world!
But once Henry's at school, the dragon's free to roam and find its intended target. Oh, the poor lunch lady!
A fun, artistic romp of a read.