Mine’s a mix of sans laziness and love for bad puns, Papyrus’s ego and loyalty towards his friends, (Temmie) Bob’s formal manner of speaking, Undyne’s inner charm, and Napstablook’s introvercy
When you first meet Napstablook cheering him on enough has him do an "attack" where he cries up and makes himself a little top hat and he says "I call it dapper blook... do you like it?"