Brain in Jar Character from the first trailer Spoiler possibly.

[caffeine4671]

Probably it was part of the original concept, demonstrated by the early beta from 2013 video (found inside the SuperSecret rar). It is from the same time as the gameplay trailer.

Froctional Games revised many aspects of the plot and setting until the final version, so most likely this part was scrapped.

It would be cool if we got to play (or at least watch) that entire early beta to see how far was it actually from the final game!

Yeah! Simon's nightmares were similar to the brain in the jar as well, at least in some aspects.

There's always the chance that a character could have a nightmare similar to the brain-in-jar thing in the Depth series/film.