Deoxys can change its form to adapt and dominant in the Speed, Defense, or Attack stats though it is usually caught with normal stats at first; the stats of the normal form are still extremely unbalanced, as the two Attack stats and the Speed stat are much higher than the Defense or HP stats. Deoxys is a very intelligent extraterrestrial creature, who travels to other worlds inside of a meteor. Very little is known of its origins, other than it is a mutation of an alien virus that was exposed to a mysterious laser. Deoxys also seems to be able to regenerate lost appendages via it's arms, and shown to have the ability to make far weaker copies of itself.
For a creature of pure logic and stoicism, Deoxys has quite a unique nature. Some can say it is vengeful, for it's rivalry with Rayquaza has been highlighted a few times throughout the series. However despite being alien in origin, Deoxys like all other Pokémon can be befriended given time.
Another Deoxys appeared in the episode "Cheers On Castaways Island!", where it transformed into a stone after struck by a thunderbolt. Near the end, it transformed back into Deoxys and protected Ash, Brock, Dawn, the Corphish and the Mantyke from the meteors that dropped down as it attacked Jessie's Yanmega.
Deoxys appeared in the movie Destiny Deoxys where the purple one tried to free the green egg trapped on the meteorite, however it was attacked by Rayquaza after being mistaken as an intruder for trespassing in its territory. They eventually had a duel somewhere in the arctic where a group of researchers witness the fierce battle between the two, as Deoxys was about to attack, the electrical surge shielded Rayquaza from its vision, giving Rayquaza the opportunity to regain strength, finally Rayquaza manage to defeat Deoxys and fly back into space, while the green egg in the meteorite was brought along by the researchers.
Four years later, the purple Deoxys had fully healed and track down its friend to LaRousse City, it causes a blackout to the entire city and remove all of the city's inhabitants in order to fulfill its search for its friend, however Rayquaza sensed its presence and headed to LaRousse City, Deoxys created a shield around the city, but Rayquaza found a way in and defeated all of the Deoxys clones. Ash and the others were able to provide enough amount of energy to revive the green egg, which hatched into the green Deoxys. The green Deoxys tried to stop the conflict, however the city's security system became haywire and attacked Rayquaza, the two Deoxys helped to defend Rayquaza, however they were overrun by the security robots, luckily Ash was able to deactivate the robot leader using the ID card, Rayquaza now convinced that they weren't intruders flies back to space, the Deoxys bids a farewell to everyone and leaves for space.
Deoxys is one of the only Pokémon to have nearly identical Pokédex entries in every game in which it appears.
It is one of the strongest Pokémon, having the 504+ of Speed (As Speed Form), Attack, and Special Attack (as Attack Form), and is capable of overwhelming many Pokémon.
Deoxys' speed form was called Flight Form when it was first released.
Deoxys' speed form was not originally intended to be released and was only a last-minute addition for Emerald. This is evident by the fact that its original three forms (Defense, Normal, and Attack) can be put into order so that the first letter of each form can spell out DNA, which Deoxys is based off. But there is also a hint with the Speed Form. The "S" in Speed also refers to the S at the end of Deoxys, because DNA spells out Deoxyribonucleic acid, where the "S" comes after Deoxy.
Although Deoxys was first obtainable in FireRed and LeafGreen, it is the last Pokémon in the Hoenn Pokédex.
Any part of Deoxys which is damaged will regenerate, as seen in the movie.
Deoxys appears in a Pokémon Dream World minigame; going into space high enough will cause Deoxys to appear out of nowhere and disappear.
Deoxys is the first and only Mythical and Event-exclusive Pokémon to be caught without the need of and event item (in Omega Ruby and Alpha Sapphire only). This makes it lose it's status as an Event-exclusive Pokémon.
Prior to Generation VI, it was an event-exclusive Pokémon, and could not be legitimately encountered in any of the main series games otherwise.
During the events of the Delta Episode of Omega Ruby and Alpha Sapphire, Deoxys intentionally changes the direction of the meteor it is traveling on midflight, and sets a new course for the Hoenn Region, thus prompting Zinnia to seek the help of Rayquaza. Its reasons for changing its course are unclear, but it is later speculated by a scientist in Mossdeep City that it was not out of ill intent on Deoxys' part.
Deoxys was given out in the U.S., Japan and Europe as movie event Pokémon, as well as a Gamestop event Pokémon in the U.S. Deoxys can also learn most of the TM moves, making it one of the most powerful Legendary Pokémon to date. It is a versatile, powerful Pokémon, learning a vast variety of moves specializing in all kinds of stats.
A glitch will occur if using a Gameshark to capture Deoxys past the event- when going to catch it a Missingno will pop up, but will have the cry of a Deoxys, as proven in Pokémon Emerald.
Wild Deoxys are always in the Normal Form.
In Omega Ruby/Alpha Sapphire if you go to Fallarbor and enter the house of the Scientist with Deoxys in your party you can change the form by bringing it closer to the meteorite it will change forms to become the Attack Form, Defensive Form, Speed Form and back to normal again.
The name is derived from the D in DNA (Deoxyribonucleic Acid), to which Deoxys looks like a strand of DNA, has an unusual capability to regenerate its damaged parts and it can multiply itself like a strand of DNA.