little-voice
Explanation
The Joke
A child asks his father, "Daddy, how do I be a good boy?" The father responds with seemingly wise parental advice: "Frankly, you should close your eyes for a moment and listen to the little voice inside." The child then hears the "little voice" which says something like "Eat worms! Chase squirrels! Bark at nothing!" -- these are the impulsive, chaotic inner urges of a small child (or perhaps a dog). The father, confronted with what the inner voice actually said, asks, "So did you hear a voice, or what?"
The joke subverts the common parental and self-help trope of "listen to your inner voice" or "follow your conscience." The assumption is that one's inner voice will provide wise moral guidance, but for a small child, the inner voice is just a stream of bizarre, animalistic impulses. The father's advice completely backfires because it assumes the child has a developed moral conscience rather than the id-driven mind of a young kid.
The Humor
The comedy comes from the gap between the father's expectation (that the child will hear the voice of conscience offering moral wisdom) and reality (the child's inner voice is feral chaos). It is a funny observation about child development -- the idea that young children have an "inner voice" guiding them toward good behavior is laughable to any parent who has watched a child eat dirt or scream at a wall. The joke also gently mocks the platitude itself, suggesting that "listen to your inner voice" is only useful advice if your inner voice happens to be sane and well-adjusted.