MAJOR SPOILERS for It: Welcome To Derry season 1 are ahead!
It: Welcome to Derry includes a chilling pre- and post-credits scene that makes one moment from It: Chapter Two so much more disturbing and tragic. Many viewers correctly guessed that Ingrid was actually Mrs. Kersh. After she sees the Deadlights in Welcome to Derry, she loses her mind, getting admitted permanently to the Juniper Hill Asylum. This leads to the credits scene, which is from her perspective.
26 years after she is admitted into the asylum, Mrs. Kersh is in her room painting when she hears a bloodcurdling scream. She goes down the hall to see that a woman has died by suicide and the woman’s husband and daughter are in complete shambles. The daughter turns to look behind her, and it’s Sophia Lillis’ Beverly Marsh.
It turns out, this is the moment that Beverly’s mom kills herself, which is referenced in the movies but never shown. In addition to being hard to watch, the scene after It: Welcome to Derry’s ending recontextualizes a moment in the second movie, making it all the more tragic.
Mrs. Kersh Is A Reminder Of The Worst Day Of Beverly Marsh’s Life

When speaking to Screen Rant’s Grant Hermanns, It: Welcome To Derry’s co-creator Jason Fuchs discussed how the prequel credits scene finally answers the question of why It takes the form of Mrs. Kersh. Fuchs stated, “Whether Beverly remembers it in that moment or not, the most horrible day of her life was the day her mother killed herself, which was also the day she first met Mrs. Kersh.”
In It: Chapter Two, it seems clear that Beverly is uncomfortable around Mrs. Kersh, and the assumption is that it’s just because she’s revisiting a place with bad memories. However, when it comes down to it, she most likely subconsciously recognizes Mrs. Kersh as a symbol of her worst trauma.
Pennywise Taking The Form Of Mrs. Kersh In It: Chapter Two Shows How Twisted He Is

Look, we all know that It is evil. He’s willing to kill children in brutal ways and cut someone’s head in half with a cleaver. So, it’s not exactly surprising that he would take the form of Mrs. Kersh when Beverly Marsh visits in It: Chapter Two.
Instead, the situation is just more sinister and tragic than it originally seemed. With the context of who Mrs. Kersh is and how she knows Beverly, it’s mildly sickening to rewatch that It: Chapter Two moment when It pretends to be Mrs. Kersh. The fact that it says, “You know what they say about Derry. No one who dies here is ever really gone," is particularly awful.
He knows that’s what the real Mrs. Kersh said the day of Beverly’s mom’s suicide, as shown in It: Welcome to Derry’s credits scene. Preying on someone’s suicide as a method of torture just feels like it’s on a completely other level of depravity. So, hats off to Pennywise for proving that there’s no line that he won’t cross.
