He is, most notably, vastly magically and physically weaker than his other variants due to his corrupted and missing data.
(For backstory/lore, visit the page for the AU itself)
His appearance doesn't differ much, although it tends to distort and glitch from time to time.
The most notable aspects of his design are his eye and scarf, as his eye is constantly leaking magical energy, and his scarf can morph into nothing more than a jittery red slash across his neck if he is pushed to be stressed. His eye flow cannot be blocked- if something were to be shoved into his eye socket and impede the flow of the magic, it would build up and cause him to die.
Black, blue, and red blips of missing data float around his body at all times, and tend to swarm around his eyes and face when he is distressed.
His voice tends to be drowned out by various electronic hisses and screeches when he makes attempts to talk.
Papyrus is warm and friendly, and always puts others before himself, despite his condition. His personality does not differ much from the usual Undertale variant of Papyrus.
However, he tends to be very defensive when he is underestimated by others, even to the extent of running from home when Sans becomes too protective of him. Despite that, he is also seen to become very anxious when separated from Sans for too long, becoming paranoid of the human's return if it gets too extreme.
Touching his right eye causes him a great deal of distress, as it triggers various vivid and nightmarish flashbacks of his countless deaths.
He loves his brother dearly, attempting to make breakfast for him nearly every morning. They're as close as two brothers could ever be. He leaves Sans small notes and gifts around the house, ranging from crayon drawings to clean socks. Sans keeps them in a small suitcase in his room. He does not have many relationships other than with his brother, as he is rarely let outside of the house. Sans fears that the bitter cold and treacherous forest of Snowdin could cause Papyrus to become even weaker than he already is.
His magic is greatly diminished due to his downgrade in strength. However, if completely afraid or enraged, he can adopt abilities from leftover bits of other Papyrus' data floating in the intangible multiverse. Along with a sample of their powers, it boosts his ATK greatly, but downgrades his HP sharply. Alongside that, this ability cannot be maintained for long, and causes him to become excessively weak and vulnerable upon its fading.