THE EVANGELION UNITS:
Eva 00 was the first Eva ever made, therefore it was also the first functional Eva. It's more a prototype than an actual fighting Eva therefore it serves test porpuse instead of real combat. It's less complicated than Eva-01. Contrary to Eva-01 it only has one eye sensor. It lacks the weaponry of Eva-01, but has the same internal structure. It comes from an Angel. It was originally yellow but after being almost destroy by the fifth Angel, it changed its armor and its color to blue and shoulder blades were added also.
Eva-01 is the most important robot in Neon Genesis Evangelion. It's the most active Eva with the best combat record. However it's still the most unstable one. It looses control a lot. It "eats" an Angel after defeating it. The weirdest detail is that it literally absorbs the body and soul of its pilot, Shinji. The main armament of the EVA-01 is a giant sub-machine-gun and two progressive knives. EVA-01 is NERV's main combat unit and is colored in deep purple and neon green.
Eva-02 was the first mass-produced Eva. It really is the first real Eva. It's the lest complicated and most stable one, but the worst one in actual combat. Eva-02's parts were manufactured in Japan but it was assembled in Germany. It is a bit less complicated than Eva-01. Instead of the two eyes Eva-01 has, Eva-02 has four. Just like Eva-01, Eva-02 has a mouth. Eva-02's design is very similar to Eva-01 design. Eva-02's main weapon is the progressive lance, but it also has a knife as backup.
Eva-03 is the second production model and was built in the US. Its pilot is the 4th Child, Touji Suzuhara who was Shinji's classmate at the time. He reluctantly accepted the position only after NERV agreed to transfer his injured sister to their private hospital.
Eva-04 was built by NERV-2 in the Nevada Desert, America. It never appeared in the series because its initial activation test went horribly wrong. Unit 04 had no assigned pilot. It is the final production model under the control of the Dummy Plug system and is believed to be similar to EVA Units 05 - 13, The EVA Series and resembles Unit 03 but white in colour.
It has been speculated that EVA 04 was built and installed with the 4th Angel's S² Engine. This was directly transplanted from the specimen that NERV was able to obtain. An S² Engine works by converting matter into pure energy without any loss. It is believed that during the activation test, the S² Engine was activated and created a Sea of Durac. This destroyed everything within an 89 mile radius, including the second branch of NERV, and converting it into pure energy. Thus EVA Unit 04 and NERV-2 were wiped off the map.
Other Evangelion units:
There are 9 other Eva units. Unit 05 - 13, are collectively known as The EVA Series. They are all identical to each other and are equipped with retractable wings giving them the ability to fly and double-sided swords. Their swords can be transformed into the Lance of Longinus - a formidable pronged weapon that can penetrate an AT-Field and destroy Angels. But since EVAs are made from Angels, the Lance if also effective against destroying EVAs.
They appear in the two movies; Death: Rebirth and The End of Evangelion. They are white with no eyes and are under the control of a Dummy Plug system derived from Kaoru whereas the Dummy Plugs for the EVAs under NERV's control had the Rei Dummy Plug system for back-up. The EVA Series were made in the G7 Nations, China and Russia under the authorisation of SEELE.
They are also powered by internal S² Engines like the Angels and so require no external power source. They were built to fulfill the prophecy of the Dead Sea Scrolls and the Human Instrumentality Project.