my problem with the forgotten man being papyrus is just what would even be the point? It would still essentially be a new character just with Papyrus's name and design similarities since they aren't alike at all. All the other Undertale characters have an almost identical personality to what they had in Undertale.

And why do people call The Forgotten Man Kris's therapist? It was pretty clear in that egg room that Kris drawing the man behind the tree was meant to be an expression of whatever trauma they went through, which would mean that Forgotten Man was likely involved in whatever happened back then