When Kitty softpaws, Humpty and puss are in the giants cloud lair, the high altitude causes their voices to raise in pitch, Humpty explains that is caused by the low pressure due to the height. However, when the trio exit the lair (when they are falling) their voices are normal in pitch and somehow not high at all.
The goof item below may give away important plot points.
Incorrectly regarded as goofs
When Puss, Kitty Softpaws, and Humpty Dumpty are up in the Giant's castle, the golden eggs are too heavy for them to pick up easily, which is why they steal the goose instead. Once they get back on the ground and are in their camp for the night, they each take one of the new eggs the goose has laid and hold it up, with one hand, to salute their victory. It's later revealed that Humpty's plan, however, was always to steal the Golden Goose itself, rather than just eggs, so the heaviness of the eggs may have been a ruse.