What specific event was the forking point between the two storylines? In Rebuild of Evangelion, the first movie is almost an exact retelling of the original anime series. But soon it begins to deviate more and more (and more /sad...), until I really wasn't sure of what I was watching anymore (but I digress).

So, lets consider both storylines as happening on parallel universes. 

What is the event (onscreen or not) in the Rebirth series that is the turning point of the forking/deviating storylines?



While this may seem opinion-based, it is not. I am asking you to compare the rebirth movies to the original series, script or storyline-wise, and backtrack the visible differences to their sources, pointing to a specific event that happened onscreen or was mentioned that may be the cause of those differences, looking backwards for the cause of that other event. Pepper your answer with references, please.

You may add a few speculations in making your chain of causality, if the events have a significant impact or relation.
Here's a list of differences between the first movie and the original timeline

The most notable plot-wise is that Misato knew about Lilith, and she knew what Lilith's purpose was, and later before the Ramiel battle, she showed Shinji what Lilith was and explained why he needed to fight the Angels.


  The appearance and identification of the Angel Lilith at the end of the first movie and just before the commencement of Operation Yashima (Corresponding to Episode 06 of the TV series), unlike the veil of secrecy kept in the original series where Lilith was never seen until Episode 15 and wrongly identified as Adam until Episode 24.
  
  More notably, Gendo and Fuyutsuki speak about a "contract with Lilith," which did not exist in the old series. Lilith's existence may not be a mystery, but its role is hinted to take a different turn from its original series counterpart. 


There was no mention of a "contract" with Lilith in the original time-line.