Evangelion

Creator Hideaki Anno admitted that Mari wasn't his idea and added her only after a request from one of the producers. However, this doesn't entirely diminish Mari's importance as a character. The point of Mari's character was to help the main cast develop. Being the only one among them without major psychological issues, Mari played the role of the person that helped Shinji and Asuka come to terms with their emotions and trauma.

The Evas are sentient cyborgs— meaning that they are equal parts machine and equal parts human. However, it is implied that due to the lack of an S² engine core, these giants require an external source of energy to operate, and are therefore technically incomplete ... Unit-01 ate the Angel Leruel to gain its S² engine core

The Evangelion Loop Theory talks about a time loop that resets the entire world after the Third Impact, over and over again. According to this theory, the movies aren't remakes but sequels set after EoE, where the world was restored with slight alterations to its original form. There are other variations to this theory...

Why did Fuyutsuki join Gendo and work tirelessly to bring about the end of the world with the Third Impact? Was it because of Yui? Let's find out!

Human Instrumentality Project is a plan to force humanity to undergo evolution by bringing the Third Impact under NERV's control. It is meant to unite all the Lilin Souls as one being after the Third Impact.