The mistreatment of Gemmy
Gemmy is a white, English kid who is the victim of an obviously traumatic life. How do his fellows receive him when he returns from the wild? They treat him as a spy and they beat him mercilessly, chasing him into the wild to die. This irony is Messianic in nature, making Gemmy something of a Christ character.
Janet's enlightenment
When Janet has her religious epiphany, it's because she gets stung by a bee. This is ironic in a few ways. It's ironic because it is actually pain that drives her transformation, and it's also ironic because the pain of a bee sting seems to be disproportionate to the effect it had on Janet. A simple bug sent Janet into her religious awakening.
The naturalized German
One ironic character is the poor, unfortunate German who came to Australia as a citizen of England, since he emigrated. He probably didn't know that Germany and England would be in WWI when he made that choice, and now, because of an ironic twist of fate, no one can tell whether he is a spy or just a supremely unlucky ex-pat.
Sir George's rejection
Sir George is ironic because his character is a depiction of the novel's main themes being rejected, within the course of the story. This might be a way of saying that only some people can ever really appreciate the meaning of the novel, and perhaps it has something to do with power.
Lachlan's toy gun
One of the first images of the novel is Lachlan holding Gemmy at gunpoint with a stick. Ironically, Gemmy recognizes the gesture, but he doesn't recognize that it's obviously a fake gun. This just underscores the perplexing nature of Gemmy's character.
