They have light world equivalents and lancer and rouxls and someone else goes into your pocket in one of the first two chapters so you probably just had their light world equivalents in your pocket
Deltarune theory: Kris is either schizophrenic or narcoleptic and parasomnia specifically the type that gives you frequent nightmares and dark worlds is either just them hallucinating or falling asleep in wherever the dark world is supposed to "be" and having a nightmare and the reason you dont see someone checking on kris after kris seal the dark fountain which could be either the hallucinations stopping or kris waking up is because you the soul your not kris your the soul so you dont see much of that stuff and sleep or if they had narcolepsy and parasomnia then them randomly collapsing wouldnt be shocking since theyd have had to do it enough times by then that its not shocking