- The Knight is a skeleton, which monsters like the Holidays don’t have
- The Knight uses attacks similar to Sans and the Starmen from the Mother series
- The Knight is strong enough to kidnap Undyne in the Light World
- The Knight left the Library in broad daylight during Chapter 2, meaning they’re someone who wouldn’t draw attention in public like Dess
- The Knight is wearing a helmet, making the antlers an unreliable detail
- Papyrus is notably absent from his house while the Knight is at the church
- After you meet the Knight, you can no longer ask Sans about meeting his brother
- There is a badge in Sans and Papyrus’s basement; the Shelter has a police badge as one of its symbols, and Undyne likely had one when the Knight kidnapped her
- The Japanese translation of Entry Number 17 implies Gaster is talking to people very close to him, likely Sans and Papyrus
- The returning cast of Undertale all have the same character arcs; Papyrus’s arc was an attempted kidnapper who wanted to become a famous knight that ultimately brings everyone together as part of a plan by someone working in the shadows
- Papyrus is described as forgettable and seems to know more about the world around him than he lets on, which is 1:1 for all of the other Shadow Crystal bosses
- There is a line in Papyrus’s boss fight (played for laughs) in which he accidentally prepares a non-bone attack
- According to the Winter Alarm Clock dialogue, Papyrus apparently constantly says that you should “reach for the stars,” and he set up a labyrinth of ice and Christmas decorations for the party (in which Asgore got trapped)