Otis Amber

Never fear the delivery boy Otis Amber is here.

"Boom" he replied. The two woman were so startled that the delivery boy sneaked up on the unsuspecting for the rest of the week, shouting "Boom" (p.83)

This shows that He likes to play silly pranks on people, to frighten people. He did it to his partner so he would act the same to everyone else.