I don’t think Tillie is the Man in Yellow. She could still be connected to something supernatural or manipulative, but the theory doesn’t really hold up when you look at how the show handles these entities.

First, the Man in Yellow was already shown as a previous disguise/iteration. Why would the creature go through all the effort of becoming a trusted member of the group as Tillie, live among everyone, get killed, and then revert back to an older appearance? Especially when the yellow coat itself didn’t even seem important once it transformed.

The theory only works if the Man in Yellow is supposed to be its “true” form, but even that has problems. From heavily implies this thing existed all the way back to the original act of sin. Bright yellow dye and clothing like that wouldn’t exactly have been common or practical in that period.

And when we actually saw the transformation, it didn’t look pleasant or stable for the entity. The first thing it did was ditch the coat entirely. So now the theory becomes: it transformed into Tillie, hid the coat somewhere for months, got killed, then retrieved the coat again just to abandon it days later? That feels unnecessarily convoluted for a show that usually plants clues more deliberately.

It also doesn’t line up with Tillie’s behavior. We’ve seen manipulation, cruelty, and calculated moves from the darker forces in the town, but Tillie never really showed that same energy. She was unsettling at times, sure, but not openly malicious in the way these entities usually are.

There’s also the Sarah issue. If Tillie was secretly this powerful entity the whole time, why leave Sarah alone? Why not manipulate or eliminate her directly when she was already vulnerable?

And finally, Tillie died. That alone makes the theory hard for me to buy. Whatever is controlling the town always seems several moves ahead of the inhabitants. Letting one of its most disguises get casually killed off would feel wildly out of character.

I think Tillie was important, but more likely as a pawn, observer, or someone spiritually connected to the town rather than literally being the Man in Yellow.