ISWM THEORY -
The dad character that begins part 2 is actually Wilford Warfstache
The theory:
This is not the water man nor a random guy, this is a character Wilford plays in his mind where he imagines and acts what having a child (us in this case) would be like - if the events of WKM hadnt taken place.
The evidence:
A- He talks about how when having recurring nightmares, the way to cure it is another story.
Then proceeds to take out books from the shelf- all of which are Markipliers previous args. From his reactions (wkm-too grisly, adwm - he's read it too many times, etc) we can tell he knows and has been watching all of them as stories (not as a person living them).
-> It fits perfectly with Wilfords powers and behaviour, being outside of reality, coping with the trauma of WKM by jumping around the other "stories" , having them phisically as such. <-
B- He has reality altering powers
1.- The explosion of light and butterflies that happens when we choose the horror book, and he throws away the Romance one.
2.- The glass of water he takes out of his fanny pack to give to us
C- The room seems like a small, perfect set, with the warm (and at parts pinkish) glow of all the small lamps, giving coziness, and it contrasts heavily with the exterior of the house we see through the door, which is left open.
The outside is dark, cold, and contrasting in colour and feel - its strange that itd be left to see if it wasnt meant to convey anything. Specially since theres a kind of cover right outside of the childs room, obscuring the rest.
It makes sense however, if this room is the only thing that exists, the only thing thats needed.
The place thats warm, lightful and calming - as opposed to the colder, more depressing outside - and reality of Will's.
We can also see just outside, a hanged yellow piece of clothing. This would fit perfectly with Wilfords pants in Motherloving (and later in this very ISWM Part 2)
D.- When we choose Horror, the full scene and illusion is cut off when Dad reads of something standing behind us, and we can see a shadow right before of the cut to black.
The shadow looks like a snake -something which Actor!Mark has been called many times, including, again, in this very ISWM Part 2.
->It could be interpreted as how Mark stopped Will (and Celine) from having their life together. (Wkm)
Just afterwards too, we hear a snarl and gory sounds, and without a warp, we are transported to "A murder with Markiplier" which is a murder investigation scene- and perfectly parallels how Mark (the snake) separated William and Celine via the events of Who Killed Markiplier.<-
Other evidence:
-Right at the very beginning of part 2, when the universe reboots, it does so on Warfstache OS, and then, after a very glitchy speed run of part 1 and warp intro, Dad is the very first character we see.
-He speaks and acts in ways that remind of Wilford/William
-Has "Dad" written on his shirt, as in proving the character he is supposed to play (in a slightly forced, cartoony way)
-Acts very caringly and prepared, as the perfect idea of a dad would (or as something rehearsed -the glass of water, the books, being just in time to console their frightened kid)
-Its the only time in all of ISWM we are not wearing our Captain suit or gloves.
-Instead of using a "gender neutral" colour for the gloves and socks of Y/N, we wear mismatched ones including pink rhombus ones, all in the chaotic style of Wilford
-WKM fitting dialogue - he talks about how romance reminds him of his mistakes and how if he tried harder he'd maybe deserve to be loved; (since he just thinks Celine disappeared without saying goodbye) and about how he's "divorced" -which could be a valid excuse in the illusion, as an explanation for why Celine isnt around anymore.
Conclusion:
Wilford might have/create illusions in which he had children with Celine, and being that his powers let him have others in/be in others minds (seen in Wilford Motherloving Warfstache, Damien) we briefly take the place of that imaginary child.
Credit to @zanda-rl for the original idea
