One kidnapping a random BFDI (specifically Black Hole) fan (henceforth known as Reader) from a different universe to her pocket dimension, expecting that either A) actually being near him or B) being in her pocket dimension would make Reader like super scared or something and thus worsen BH’s mental state to make it easier for her to manipulate him or something BUT! Reader instead starts freaking out in a GOOD way and is like “wait actually this is so fucking cool”
And BH is thinking “who is this? Why do they seem to know where we are? And why the ever-loving void do they seem to have zero fear in this situation” and then he gets extremely flustered when Reader sees him and starts gushing about how cool they think he is. There’s no way he wouldn’t get super flustered from praise, the guy’s received like maybe 5 compliments total in his unknowably long unlife
Meanwhile One was surprised that Reader’s freakout was from excitement but then became so unbelievably happy when she realises that! Reader complimented something she made! Reader likes something she did! And most importantly, Reader said all that without even knowing One was there, so there’s no way Reader could’ve been just saying that to flatter her!
(Well, Reader had a suspicion she was there and watching for something because otherwise what reason would she have to kidnap someone from a completely different universe. But One never has to know that)
Anyway Reader gets on the topic of BFDI lore after Black Hole asks where they’re from, and then One reveals herself so she can ask questions to an “expert” on the contestants because “that stupid leaf acted nothing like she did in the show”. This causes Reader to summarise BFDIA, which causes them to go on like 2763 tangents and somehow pulling out a big whiteboard to help them make and organise their points as they question if all objects are able to make an evil version of themselves with enough anger and loneliness
It’s when Reader starts trying to compare the goop all over the place after TPOT 19 to the Horrifying Sludge from BFDIA that BH and One start to think they’ve lost the plot (who’s being referred to with that they? Yes). After stopping the impromptu lecture, One says she “doesn’t know how to send Reader back to their universe”. She’s not lying, but even she did know she’d keep them around because they’re the first person she knows of that has complimented something she did/made, which she counts as indirectly complimenting her. Black Hole is secretly, maybe selfishly, pleased that Reader will be sticking around because in one hour they singlehandedly doubled the amount of praise he’s gotten in his entire unlife
Eventually they all get together and Reader says “i’m their third” and they kind of are. But in the same way that the front wheel of a tricycle is the third wheel. Reader is the reason One and BH’s relationship was able to be driven from enemies to lovers