The BFG and Sophie have nothing in common — different sizes, backgrounds, abilities — yet they form a genuine and tender friendship. Dahl suggests that real friendship transcends all superficial differences.
The BFG is mocked and bullied by the other giants for refusing to eat children. He is different from his peers and suffers for it. Dahl presents his gentleness not as weakness but as true moral strength — the BFG is the best of all the giants precisely because he is different.
The BFG speaks in a wonderfully muddled way — mixing up words, inventing new ones, speaking 'gobblefunk'. Dahl presents this as charming and creative rather than deficient. The BFG's language is part of who he is, and Sophie never corrects or mocks him for it.
Dreams are central to the BFG's world. He collects and classifies them, understanding them as real and important. Dahl suggests that imagination and dreams are genuinely powerful — the BFG's dream-mixing ultimately saves children across the world.