some of my favorite trends in Undertale fanart:
papyrus’ jaw sticking out at odd angles when he’s yelling
mettaton hugging people by wrapping his noodle arms around them like 34 times
sans with a definite belly, no explanation given
frisk using asl (and all the monsters understanding it)
that post-pacifist au where frisk keeps flowey in a flowerpot and he’s just a whiny little shit
toriel with a slightly dragon-like appearance
sans hiding things in his jacket
papyrus and toriel picking sans up when they hug him
papyrus being amazing at helping people thru panic attacks
undyne with impossibly long flowing hair
undyne’s “hair” actually being a fin
sans with a gap in his front teeth
alphys’ pudgy little tail
mettaton/napstablook bonding
chara as the provider of the game’s flavor text
sans treating the gasterblasters like pets
sans instantly falling asleep in weird places (usually papyrus’ arms)
god of hyperdeath = asriel’s totally original OC do not steal
asgore hastily naming asriel by mashing together his and toriel’s names
gaster being really sweet and gentlemanly before The Accident