The most obvious moral lesson is the importance of honesty. By never lying, characters in the story uphold their integrity and gain the trust of others.
One important lesson is that honesty builds trust. Just like in the stories where people who told the truth were trusted more in the end. Another lesson is that it gives you a clear conscience. If you lie, you might always worry about being found out. But when you are honest, you can be at peace with yourself.
The moral is that honesty is always the best policy. When you never tell a lie, people trust you more. For example, in the story of the boy who returned the wallet, his honesty made the owner trust him and society becomes a better place when everyone is honest.
One possible moral lesson could be respect for the unknown. Since griffins are often mysterious creatures, the story might teach that we should respect things we don't understand.
One possible moral lesson could be that honesty is the best policy. Since it's a story about a liar, it likely shows the negative outcomes of lying.
A do not tell a lie story also teaches responsibility. By not lying, the characters are taking responsibility for their actions. For example, if someone breaks something and tells the truth, they are accepting the consequences of their actions, which is a sign of maturity and good character.
One possible moral lesson could be about not judging by appearances. Just because a character has a pumpkin head doesn't mean they are bad or evil.
One possible moral lesson could be about hospitality. Just like offering a cup of tea is a sign of welcome in many cultures. If a story has characters sharing or refusing a cup of tea, it might be teaching about being kind and inclusive.
One possible moral could be the importance of listening to wise advice. If the king in the story is foolish because he ignores the good counsel of his advisors, then it shows that we should be open to the wisdom of others.
One possible moral lesson could be about respect for the divine. If the story revolves around the name of God, it might be teaching that we should hold the concept of God with great respect.
It might teach about responsibility. Superman has a great sense of responsibility towards the world. In the 'superman and me short story', characters could learn that with great power or ability (even if it's not superhuman), comes great responsibility and should act accordingly.