Dinkin Dings and the double from Dimension 9

Dinkin Dings, a boy who is afraid of everything except The Frightening Things--the ghost, the monster, and the skeleton who visit him every night--meets Danger Dings, a boy from the opposite world of Dimension 9, and Dinkins finds he is the brave one for a change when The Actually Frightening Things from Dimension 9 come in search of Danger.