In The Wizard of Oz, the Scarecrow, the Tin Man, the Lion, and Dorothy ask the Wizard for a brain, a heart, courage, and a way home, respectively. The Wizard refuses to grant their requests until they have brought him the broom of the Wicked Witch of the West. So the characters set off, kill the Witch, and return to the Wizard to present him with the broom. At this point, the Wizard starts stalling and demands that they come back tomorrow. He only acquiesces when it is inadvertently revealed that he is not the giant, disembodied head the characters have been talking to, but rather an ordinary man operating the head with a machine.
The real Wizard turns out to be a self-described "good man" who readily gives Dorothy and her friends everything they want: he has on hand a number of educational diplomas, one of which he gives to the Scarecrow, and a heavy cloth bag that is presumably full of awards and trinkets, of which he gives one each to the Tin Man and Lion. He also reveals that he has been keeping a hot air balloon ready for a return trip to Kansas.
Given that the Wizard had already prepared everything Dorothy and her friends asked for (or at least coincidentally had all them within arm's reach or just outside), why did he stall after receiving the broom? Why didn't he, in his persona of the disembodied head, acknowledge that the task he issued had been successfully completed and arrange for the awards to be presented more or less immediately? Is there any sensible story-internal explanation for this?