Mumm-Ra disguises himself as an innocent Berbil to try and defeat the ThunderCats. He plays upon their altruism to gain entrance into the Lair. Once inside, he casts a spell on them and, seizing them with slave bracelets, he transforms them under his command. Mumm-Ra's plan almost succeeds, when only Lion-O is left unaffected by the spell. Lion-O chooses not to use the Sword's powers against his fellow ThunderCats, because he believes in their ability to remain true to their real identities. Instead, he flees in order to fight Mumm-Ra alone with the Sword of Omens. In battling him, Lion-O calls forth the Sword's power. His faith in the ThunderCats proves well-founded, because their response to the Sword's emblem is stronger that Mumm-Ra's spell, and they free themselves from the spell. Returning to Lion-O's aid, they help him defeat Mumm-Ra.
What a person is really like is based on his personalities, which are his characteristic patterns of behavior and modes of thinking in reacting to the environment. Lion-O was tested when the other ThunderCats turned against him. But because his friendship was based on his knowledge of his friends' true personalities and not on superficial characteristics, he did not lose faith in them. If we choose our friends in this way, we can believe in them in times of crisis or when we hear misleading things about them, because we will know what they are really like. And because personality tends to be consistent over time, if we choose friends carefully, we can expect our friendships to last and be rewarding over a long time.