The cloud's strange powers
Despite appearing to be a normal cloud, the Cloud of Doom moves items around different floors in the school. This is another example of personification and a paradox: viewers don't expect the cloud to have human-like characteristics. Not only does this make the cloud more ominous, it makes it more threatening. After all, if a cloud can get up and walk around like human, it can do anything.
Sticking by friends
The quote "it is harder to stick by a friend who is up [rather than down in the dumps]" is ironic because people often say and believe that sticking by a friend is often easier when they are up. By including this quote, Sachar plays on readers' preconceived notions about friendship and loyalty. He also injects humor and levity into the work.
Mrs. Jewls' lesson on a million
Mrs. Jewls decides to collect one million toenails to illustrate what one million means to her class, despite the physical impossibility of collecting so many toenails. Sachar includes this irony to emphasize how zany and creative Mrs. Jewls is.
D.J.'s hiccups
Despite the fact that he cannot control them and although hiccups cannot speak, Kathy argues with D.J.'s hiccups. This is paradoxical: hiccups do not produce language and are unintelligible. Because of this, readers don't expect Kathy to argue with hiccups. Sachar includes this irony as a way to add humor and intrigue to the story.
