!Spoilers for Chapters 3 and 4!
(Only about the secret eggs, but still)
I haven't seen anyone mention this yet, but maybe I missed something.
The Man in the egg room in chapter 3 says this schedule:
"On Thursday, I go to sell the donuts.
On Friday, I toss the leftovers in the dumpster.
On Saturday, I let it cool on the windowsill.
On Sunday, I harvest the wheat.
Hold your breath, head to the left, and count backwards to 100..."
While "hold your breath" bit makes me think of the Knight fight and Kris's Act, I haven't checked anything, so I have no idea if there's anything.
However, I noticed something about the schedule that makes me think that this could be instructions on how to get the egg in Chapter 5.
Chapter 4 happens on Saturday, so Chapter 3 is happening very early on Saturday, Chapter 2 is Friday and Chapter 1 is Thursday.
In Chapter 1, while the egg room itself is not adjacent to Bake Sale, it is the room you are returned to after exiting the egg room, rather then the Starwalker room. Extra note, in Bake Sale there's a Hathy selling donuts.
In Chapter 2, the egg room is next to the room with the dumpster.
Chapter 3 itself is somewhat skipped in the schedule, bit that's probably because it is between two days.
In Chapter 4, the egg room is found in the windows hallway.
All of this correlates to the schedule.
"Sell the donuts", "toss in the dumpster", "on the windowsill".
So the conclusion would be that in Chapter 5, that should be happening on Sunday, we should look for something related to harvest or wheat to find the next egg.
I really hope that I'm onto something there, but there are some holes, like chapter 3 being skipped or the Bake Sale being somewhat of a stretch.