Playbacktale is an Undertale AU comic created by Linssins. It takes place before Frisk fell into the Underground. In the comic, Papyrus, Flowey, and the 6 human souls accidentally fused creating "Playback Papyrus" or PBP for short.
This is the original 20 page comic. It begins with Papyrus and Flowey hanging out in the Snowdin forest. Flowey asks Papyrus if he's ever wondered what not having a soul feels like. Flowey then admits that he does not have one, and Papyrus offers to help. They both go to Asgore in order to ask if they could borrow a human soul. While Papyrus is distracting Asgore, Flowey tries to steal all 6 souls. Papyrus stops him before it's too late, but not without consequences. They all accidentally fuse into an amalgamate being. Sans, who was sleeping in Snowdin, receives a strange call. He realizes that it's his brother's distorted voice saying that he "made a huge mistake".
This is the second part of the comic. Flowey, now with Papyrus' soul, struggles with his newfound emotions, showing obvious regret for his actions. Papyrus, however, does not feel anything. Meanwhile, Sans is trying to find Papyrus and stumbles into an echo flower clogged waterfall in Waterfall. He blasts through the flowers, and finds an unresponsive Playback Papyrus.
Within their subconscious, Papyrus and Flowey continue to talk. Flowey is afraid of Papyrus at first, because now that they are merged, Papyrus knows what Flowey did in the past timelines. Flowey believes that Papyrus wants revenge, but accepts it, thinking he deserves it. Papyrus grabs Flowey, but instead pulls him into a hug, stating now that he, himself, is soulless, he understands why Flowey did what he did. Papyrus says that what Flowey did was inexcusable, but as long as he is sorry, Papyrus will forgive him.
They wake up to Sans sitting down next to them. Sans believes that this will fix itself when the anomaly resets, and says that he wouldn't mind doing absolutely nothing while waiting, at which point Playback bonks him with the integrity hand, and asks if that's "supposed to be funny, bro?". Sans stares at Playback, then goes in for a hug which they return, leaving Sans with a little bit of Patience on his head as well as the Integrity. As they separate, PBP's body sticks to Sans with Amalgamate-like goopiness, which Sans, of course, makes a pun about. Sans gives his acceptance of his brother's new state, saying that Papyrus is allowed to make mistakes, and it ends with them seeing if Alphys could help.