I was, unfortunately, entirely correct that watching Late Night with the Devil would make me want to write a Deltarune au based around Tenna's late night show featuring:
Instead of the (imo? Bad lol), exposition dump at the beginning of the movie where the TV host was involved in a cult to start his career and implied sacrifice to make it happen, Tenna made a deal to keep being seen by the lighteners.
This expanded the Dark Worlds into each other, and effectively collapsed the town into that dark place Undertale style. Many lighteners died, but the rest were scattered around the now unified dark-and-light world
One of the survivors was Kris.
Spamton as a puppet of [Hyperlink Blocked] is Kris' handler, and sort of Reigen-style reinvented himself as a parapsychologist to Get Big. When Kris is possessed by the "Mr Wriggles" (the player), Spamton is really just putting on a show and he knows it (yikes dude!)
Depending on the "route," it really could all end in one night like in the movie lol but it could go on as a regular feature of the TV show with various other characters coming in as guests and with Kris as a semi-main event. This would give Spamton and Tenna time to uh work together (they are actually fucking and both into this for the ratings, also like the movie).
This would also give Kris time to get to know one of the other lightener survivors who's around the studio a lot and who seems to be his age.
Susie is adopted by Tenna after the collapse, he found her afterwards and took her in out of guilt so he tends to be overly permissive in his parenting. She, like most people, has no idea about what he did. He has nightmares about her finding out and leaving him.
If Kris DOESN'T kill everyone in Hour One of this insanely bad idea of a show, it's because of Susie. She probably does bully them until some freaky or whimsical other adventure happens and they bond over their shared desire to break shit and say bad words on air.
Everyone working on the show is Very Concerned about this clearly demonic kid but they're besties with their bosses daughter so they just have to deal with it (sorry Mike).
Possessed Kris turning red eyed to Tenna: "We go way back. We met amongst the yellow flowers, remember?" And Tenna is SHOOK
I don't knowwww that Kris would need to be possessed to, say, out them and their friend's guardians on live television and cackle while calling them slurs to the shock of the audience, but even in Whimsical Fantasy 1970s TV Land that would be enough for Spamton to lose it and slap them
I wish I could draw lol because there are some great bits in that movie that could be put to the UTDR format. Eh maybe I'll edit something together using the TV World set but that'll be another night.