The protagonist of Don't Escape 2 is an older version of Cody.
It's implied that the universe of the second game is canon to the Don't Escape multiverse; on the website
for Sidereal Plexus, there's a list of worlds to which traveling is forbidden, including a universe suffering from a "worldwide pandemic of an unknown rage virus." Assuming that this pandemic is the cause of Don't Escape 2's Zombie Apocalypse, and that the dream Cody has about zombies chasing him on day 3 is real, then we could reasonably assume that he was experiencing a memory from the eyes of Don't Escape 2's protagonist; himself.- The bed underneath Cody's in Deeper Sleep belongs to a kid named Willy. Could that be Bill?
The giant eye you briefly see in Don't Escape 3 is a Shout-Out to Jacksepticeye
The same game also contains a Shout-Out to Markiplier with the pancakes, so why not?- Yes, it's possible, but it's not likely. Both because creepy disembodied eyes are common in tropes, and the Markiplier shout-out was likely just because Markiplier had been playing other games in the series at that point.
the protagonists of games 2-4 all have some form of time manipulation
They only have to worry about spending time whenever they're either moving a long distance or doing some strenuous task, besides that, they don't lose a minute of time. How else can you explain it? A later scriptwelder game will have the 4 Days to Survive cast taking action against Sidereal Plexus.
Likely as a background event mentioning a protest/lawsuit against the company organized by them. A later aniversary edition update of Don't Escape 4 will have a new ending where you take Sergent McWillis and his men with you on the spacecraft.
Should this be implemented, this can be triggered by persuading Sarge and his men to camp inside and investigate the Sidereal Plexus building during night 3. Afterwards, they will have a change of heart regarding your stance against the company and will offer to assist in preparing the rocket for launch. In turn, the requirement to hold up to five more people will prompt the player to perform a more thorough investigation of the spacecraft while using Paul's engineering expertise and more of the spare parts from the crashed plane to help you.
- Combining this with the above theory, this will lead to a new ending that teases a new scripweilder game where there are more witnesses able to testify against Sidereal Plexus for their actions.
The severely increasing numbers of Shadow People...
...are all the real people who met their demise in all alternate worlds doomed by Sidereal's meddling.