I think Error's puppets are also super interesting and I don't see many talking more in-depth about them. Yes, obviously he is so fucking nuts and lonely he started talking to inanimate objects. But the way he uses them? He has (in the canon story) two main puppets who he talks to. The Sans puppet and the Fell puppet (he does have a chara one, but they're not integral to this analysis). The gag of it all is obviously his hatred to Fell, but I think this can be interpreted more deeply. The Sans one, his supposed "friend" rejects him ironically. Mind you Error is the one controlling what they say and do. The Fell one is usually always there saying how "well I am still your friend!", but Error rejects HIM. Obviously, unlike actual relationships, he CAN control puppets. So why does he not make all of his puppets be utterly smitten with him? Those puppets are more reflections of himself than anything else. He masks his low self-worth through self-grandeur, which he sometimes accidentally reveals (think "abomination #1", or even the instance where he admits to putting Papyrus above him. He sees himself as lesser). His puppets also showcase this self-loathing behaviour even further. Even though he is the one in control of them, Sans rejects him. He imagines having a friend (Sans) and then he ruins it himself. His self-worth is so low, he can't imagine anyone actually wanting to be his friend without eventually leaving him. This can also be interpreted as self-sabotaging behaviour. Since he is the one in control, him rejecting a version of himself, is just further instilling the idea that "no relationship lasts forever". The Fell puppet is basically just another version of this "rejection". This time the "friend" is the one offering companionship, but Error rejects it. It is at the same time to assert control, as in "I CAN reject him, I have the OPTION to" (which he really doesn't but don't tell him that). But it is also again self-sabotaging behaviour. In his mind it is either: 1. People will eventually leave me because I have no value. 2. There is no way anyone sees value in me, therefore said "friendship" must've an ulterior motive behind it. He WANTS friendship (as he does see the Sans puppet as his friend) but he basically predicts this friendship falling apart. I also think this might be "comforting" to him in a way, because he has been isolated for so long he basically has no idea how actual relationships function. He can't think beyond "rejection", "rejection" to him is predictable and expected. He doesn’t just lack relationships, he can’t conceptualize one that doesn’t end in rejection.
