Chao have seven different stats, which can be increased by giving them animals or Chaos Drives. When you pick up a Chao, you can view the numbers for five of those stats; the other two, Luck and Intelligence, are hidden from view. Stats are one of the most important things for you to focus on if you want your Chao to compete in the Chao Stadium.
Each stat has four sub-components: grade, level, points, and bar. All of them can be seen in the information window when you pick up your Chao, with the exception of the grade, which can be seen by visiting the Chao Doctor in the Kindergarten.
Each one of your Chao's stats has a grade assigned to it, which indicates your Chao's natural skill and maximum potential in that area. From lowest to highest, the possible grades are E, D, C, B, A, and S.
When you level up one of your Chao's stats, its stat points will increase by an amount depending on your Chao's grade for that stat. This difference adds up significantly by the time you reach higher levels, meaning that a Chao with an S grade can end up with stat points for level 99 which are much, much higher than a Chao with an E grade. You therefore want your Chao's grades to be as high as possible.
Your first Chao will have its grades randomly assigned. A bred Chao will have its grades randomly chosen from the grades of its parents. A Chao that reincarnates will keep its previous grades. There is only one way to actually improve a Chao's grades, and that is through evolution. When your Chao has its first evolution, the grade associated with that type will increase by one rank, unless it is already at S. For example, a baby Chao with all-C grades that evolves into a Fly type will have its Fly grade increase to B, while the rest remain at C.
This means that you can raise one of your Chao's grades by one rank per life, making an all-S Chao a possible but lengthy task. When you are first starting out, it is recommended to first check your Chao's grades with the Chao Doctor, and then raise it into the type for which it has the highest grade. This will ensure that your Chao is very good at what it does.
There is an advanced section dedicated to Grades, and max grade/stat Chao.
Each one of your Chao's stats has a level, which starts at 0 and ends at 99. The level itself doesn't actually do anything; your Chao's current level of ability in a certain stat is determined by its stat points. However, once your Chao reaches level 99 in a stat, you will no longer be able to raise that stat any higher. At that point, the stat is at its maximum level for that Chao's current life. When your Chao reincarnates, the level for each of its stats will be reset back to 1 (not 0!).
Each one of your Chao's stats has a points number, which starts at 0, ends at 3266 for the non-hidden stats, and ends at 4000 for the hidden stats. This is probably the most important sub-component of a stat; it is, after all, the one that actually decides how good your Chao is in that area! A higher points value will make your Chao more capable in races or karate, giving it a better chance of winning. This value will increase when the stat levels up, by an amount dependent on the stat's grade. When your Chao reincarnates, it will retain 10% of its stat points, rounded down to the nearest 1. For example, a Chao with 1000 Swim points will have 100 Swim points after reincarnation. A Chao with 1009 Swim points will also have 100 Swim points after reincarnation.
Each one of your Chao's stats has a progress bar towards its next level. This is a percentage from 0% to 100%; however, the game just displays this as ten small squares, which show the progress rounded to the nearest 10%. For example, anything between 15% and 24% would just show as two filled squares in the Chao's stats window.
As you give animals or Chaos Drives to your Chao, the progress bars for each stat will fill or unfill slightly depending on which exact one you used. If a bar fills completely to 100%, that stat will level up (unless it is already at level 99). When it levels up, the bar empties again, the points will increase by an amount dependent on the stat's grade, and the level will increase by 1.
As stated earlier, Chao have seven different stats. Each one of these has different effects, making your Chao better or worse in different areas. These seven types are explained below.
This stat determines how well your Chao can swim, or if it can swim at all. It is therefore very important for races that contain a lot of water, as a low Swim stat will cause you to lose your position to the better swimmers. An extremely low Swim stat will mean your Chao can't even swim in the Chao Gardens, and will instead thrash about in the water!
You can increase the Swim stat by giving your Chao animals and Chaos Drives from the yellow group. A Chao first learns to swim when its Swim stat reaches 100 points, and improves it's swim style at 668 points.
This stat determines how well your Chao can fly, or if it can fly at all. It can be very useful in races where your Chao has to jump down from a height, as it can use that opportunity to pull ahead if its Fly stat is high enough.
You can increase the Fly stat by giving your Chao animals and Chaos Drives from the purple group. Chao may fly in the garden once they have 100 fly stat points.
This stat determines how quickly your Chao can walk or run, or if it can walk at all. It is probably the single most important stat for races; nearly all the races have a huge emphasis on running, and your Chao will have a significant advantage if it has a high Run stat. An extremely low Run stat will mean your Chao can only crawl very slowly across the ground.
You can increase the Run stat by giving your Chao animals and Chaos Drives from the green group. A Chao first learns to walk when its Run stat reaches 50 points, and its walking speed increases at 667 points, and 1338 points.
This stat determines how strong your Chao is. It is mostly needed for climbing cliffs in the races, where a higher Power stat will allow your Chao to climb up faster. Some races also have trees which require strength from your Chao in order to shake a nut down before proceeding.
You can increase the Power stat by giving your Chao animals and Chaos Drives from the red group. In Chao Karate, you Chao will imrpove it's punch/kick style when it reaches 400 power stat points.
This stat determines the physical constitution of your Chao. It is one of the most important stats for races, as it determines the size of your Chao's energy bar. Your Chao's energy will decrease throughout the race, and if it runs out, your Chao's speed will drop immensely. You can also cheer for your Chao during the race using the trigger buttons, which will give it a temporary speed boost in exchange for a chunk of energy. What this all means is that a high Stamina stat allows your Chao to keep its speed level and get additional speed boosts!
You can increase the Stamina stat by giving your Chao any kind of fruit, either ones that grow on trees in the gardens or ones that you purchase from the Black Market. The Mushroom from the Black Market will raise Stamina significantly, but costs 300 rings.
As one of the hidden stats, not much is known about Luck. However, recent research within our own community has revealed some facts. All animals and Chaos Drives will increase this stat; Chaos Drives boost it twice as fast as animals do. It is used on some races, where your Chao must choose a lane to run down: if it chooses the wrong lane, it will fall down a hole and probably lose its position. Having a higher Luck stat helps to avoid this. There are many rumours about this stat; see the Rumours page for more information.
As one of the hidden stats, not much is known about Intelligence. However, recent research within our own community has revealed some facts. All animals and Chaos Drives will increase this stat. It is used on races, where your Chao must solve puzzles such as a shape game or jack-in-the-box. Having a higher Intelligence stat helps your Chao to solve the puzzles much more quickly, allowing it to continue on with the race sooner. There are many rumours about this stat; see the Rumours page for more information.