[He nods enthusiastically. It's the most like Will he's looked so far.]

Yeah. You know when it shifts, it feels a little bit like an earthquake? Something like that happened earlier. I know we decided Vecna probably isn't here, but what if something weird happened with Felfri?

[He has literally never said anything about earthquakes in relation to the Upside Down, but it very much feels like something he believes. This doesn't seem like Will playing a joke at all. He's not a good actor and he does seem genuinely concerned about whatever he's trying to convey.]