Is there a problem?

twelve episodes, twelve contestants - a mix of annoying middle aged sci fi authors, fan fic authors and random people off the street

a variety of against the clock writing tasks, big finish scripts, ability to interact with actors without shouting at them and challenges where you have no budget or doctor for an episode

judged by solely by christopher eccleston

The characters immediately assume that Mr. Whatsit is Henry, but the twist is that Henry is doing it physically THROUGH Will. As in, Will is being intermittently possessed and seeking out these kids, and doesn't realize it. He experiences time loss and repeatedly ends up in places not knowing how he got there but chalks it up to sleep deprivation due to nightmares and is too afraid of seeming like a burden to mention it to anyone.

Holly is then the first victim because she lives under the same roof as Will, making her the closest target. Will and Holly get close over the 18 months of living together and regularly spend time playing games alone, where Henry takes the opportunity to take over. Holly thinks that these moments where Will introduces himself as Mr. Whatsit (he doesn't give the name Henry because why tf would he do that) is some sort of roleplay game, so she plays along and invites her friends to join in on the "game," expanding Henry's pool of victims (ig in this world Derek is either a friend or learns about her "game" and makes fun of it). Holly (and the other kids) think it's a fun secret between her and Will, so she doesn't tell anyone that Mr. Whatsit is Will. It's not until they capture Derek to protect him and he refers to Will as Mr. Whatsit that the pieces start to fall into place, and Will slowly regains memories of what Henry made him do.

The kids, once captured by Henry, under hive mind influence, don't notice that Mr. Whatsit doesn't look like Will until Holly runs into Max and Max helps her see that Mr. Whatsit isn't a friend at all.