CAUTION!!!
Really freaky, fucked upc disturbed, and just downright WRONG stuff ahead, please oh please turn back if you're not of iron will, titanium stomach, and adamantium maturity
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Still here? Ok then
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Catchy tune right?
That's about the best part of the 1995 Neon Genesis Evangelion
Series, the fucking theme song.

Everything else is a complete and total mindrape. No joke, I used to compare an anime's 'darkness' on a scale of :
0-Yuru Yuri
1-Lucky Star
2-
3-
4-
5-Magical Girl Lyrical Nanoha
6-Mai HiME
7-
8-
9-High School of the Dead
10-Puella Magi Madoka Magica

But I think I'm gonna revise that list

20-Neon Genesis Evangelion

Yup, that's right, I consider NGE to be TWICE as dark as Madoka Magica. I didn't even think that was POSSIBLE!
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When you first start watching, you might think "oh cool, a mecha anime other than Gundam!"

Then within 3 minutes after the start of the 2nd episode, this happens:

Uhm...is that a literal fountain of blood?
...
...
...
Coming out of a ROBOT?!?!?
This scene repeats soooo many times through the series, like this one in the second reboot movie:

And things go downhill from that point on, culminating in an absolute troll of a final 2 episodes, and a movie with a more than questionable first scene that takes place over the female leads hospital bed, where she lies comatose:

Use your imagination, you'll figure out what's going on here soon enough

And the movie goes even FURTHER downhill from there, ending with piles of clothes surrounded by puddles of orange goo all over the planet, a massive quasi-deity-person thing larger than the moon slowly dismembering itself, and 2 people lying on a beach surrounded by said "thing's" blood.

Now, the 2013 reboot of the series isn't as bad, it's still pretty screwed up, but much less so. Not to mention the animation is far superior in the reboots

Now, if you're still interested in watching the entire series, including the original, I recommend watching it in this order:
Neon Genesis Evangelion (1995)
(Skip episodes 25-26, they have absolutely nothing to do with the plot)

The End of Evangelion (movie)

Evangelion: 1.11 You Are (Not) Alone (2013)

Evangelion: 2.22 You Can (Not) Advance (2013)

Evangelion: 3.33 You Can (Not) Redo (2013)

The final three entries are the 2013 reboot movies of the original series, and whilst 1.11 is basically exactly the same as the first few episodes, the better animation quality makes It worth the watch,

Original ^

Reboot ^
2.22 is where the plot starts to diverge, and 3.33 is absolutely nothing like the original series (which in this case, is definitely a good thing)
So set your AT Fields to max, and enjoy, Eva Unit-01! Move out!