The Code of Thundera is the set of moral principles that governs the ThunderCats' behavior at all times. The ThunderCats strongly believe in this Code and they will do anything to uphold it. They follow it implicitly at all times and even spread its good value among other beings that they encounter.
Every Thunderian is familiar with the Code of Thundera and after the destruction of Thundera, the ThunderCats took it upon themselves to spread their Code to the inhabitants of their new home, Third Earth.
The Code of Thundera is made up of the following:
The ThunderCats strive to ensure that justice is done for all the beings that they encounter. They have taken it upon themselves to be the sworn protectors of all good beings on Third Earth and fight hard to make sure that no one is persecuted in any way. Due to this, the ThunderCats often find themselves at loggerheads with the evil beings such as the Mutants, the Lunataks and Mumm-Ra who take great pleasure in tormenting the innocent natives of Third Earth.
The ThunderCats swear to speak the truth at all times. Making false promises, claims or accusations is strictly forbidden. Honesty is one of the defining characteristics of the ThunderCats. It is what makes the other beings believe in them and their goodness.
On some occasions however, the younger ThunderCats like WilyKit, and WilyKat have been shown to lie. They sometimes do this to cover up their mistakes or mischief and because they fear the adult ThunderCats. However, they are honest enough to later on admit the truth, especially when the situation becomes serious.
The ThunderCats at all times honor their friends, family, elders and other good beings. They never ignore or disregard another good being. Whether a good creature is big or small, weak or powerful, the ThunderCats will not belittle them in any way nor will they show any kind of bias or preference when helping another being.
The ThunderCats' most important characteristic is showing loyalty at all times. They are loyal to their family, friends, and allies at all times. The ThunderCats will never ignore a cry for help or desert someone in need. They are united in their allegiance and devotion to their Code and to each other. Unlike the Mutants or the Lunataks who will not think twice about double-crossing one of their own, the bond between the ThunderCats is very strong.
Interestingly, it appears that the Loyalty that the ThunderCats have to each other is not a choice of their own but rather the result of one of the Treasures of Thundera known as the Chain of Loyalty. This chain is responsible for the loyalty between the ThunderCats and as long as it remains intact, so will their allegiance to each other.
There was once a time when the Chain was accidentally broken in a struggle between Lion-O and Mumm-Ra and as a result, all the ThunderCats started quarreling with each other. Surprisingly, Lion-O was not affected by this. Only after the Sword of Omens repaired the broken chain, did the ThunderCats' Loyalty towards each other return.