Even though the ghosts' original names were never quite revealed, I just make the assumption that Napstablook's cousins are Hapstablook (Mettaton) and Madstablook (Mad Dummy). I personally believe Napstablook was in the dummy in the Ruins all along, which is why I don't include a 4th cousin.

Napstablook wasn't quite sure how he ended up at Alphys and Undyne's house, but he mentally thanked Mettaton for giving him directions. Just a week ago, Undyne had asked to borrow one of Napstablook's CDs to listen to, most likely trying to get more acquaintanced with the ghost in some form. Seeing no harm in it, Napstablook accepted her request, but now he was coming back to return it home.

As Napstablook headed up to the door of the house, he happened to pass by a dummy that was sitting in the yard. He gave it a glance as he flew by, but once he came face-to-face with the door, he froze in place.

Blinking for a moment and deciding not to knock just yet, Napstablook gradually turned around, facing the dummy. For a moment, he swore that it moved a bit, almost as if it flinched when he had passed by. Slowly floating over to examine it further, Napstablook's eyes widened when he noticed the dummy was actually trembling quite a bit.

"H...hello...?" the ghost whispered anxiously, bracing himself for some sort of reply.

No answer. The dummy forced itself to stand still.

Napstablook couldn't quite shake off this feeling of déjà vu...like he had somehow seen this dummy before. Not only that, but something about all the rips, tears, and stitches reminded him of someone else...

Suddenly, it hit him. Napstablook's eyes would've popped out of their sockets if they could, and his mind went berserk as he berated himself for not noticing sooner.

"M-Maddy?"

A violent shake coursed through the dummy.

"Is that...you?"

"I TOLD YOU NEVER TO CALL ME THAT!" The dummy suddenly exploded, scattering cotton everywhere.

Napstablook cowered back in embarrassment and disbelief. "It...it really IS you..." He turned bright red, remembering that it was the same dummy he had cried on when trying to say 'hi' to Frisk one day. However, the mad dummy seemed oblivious to that memory, to his relief. "S-sorry...it's just...been so long…I didn't recognize you..."

"I know. I KNOW! I…know..." Mad Dummy scowled, but his tone softened. "To be honest, I…didn't think I'd ever see you again..." he quietly admitted.

"I missed you...Mad..." Napstablook looked at the ground. "I'm so sorry I didn't try looking for you sooner..."

"There's a bunch of dummies around here; I understand how it'd be difficult," Mad Dummy cut in. He blinked for a moment, realizing that there actually weren't many dummies, but shook his head. He turned around and muttered, "I'm…sorry I never came back. I just thought...y'know...it'd be...painful for you."

"…Painful?" Napstablook was confused.

Mad Dummy whipped his head towards him. "I was hoping you'd forget about me!" he snapped, but he regretted his outburst when Napstablook flinched. He lowered his voice. "I…mean...after I heard Hapsta left, I didn't want you to remember me. I've been gone for so long already! I didn't want you to see me and only be reminded of another person that left you."

Napstablook couldn't believe his words. "But...Mad…I could never forget you."

"I know. I know! I KNOW!" Mad Dummy trembled with rage. "I'm a jerk!" He tried to turn himself around, but after failing, he simply hopped to the side. "I—I just—I couldn't handle—everyone just—ARGH!" He banged his head against a tree, furious with himself for not being to form coherent sentences. "I was weak, okay!? And having a body at the time was the one solution to all my problems! Not to mention I didn't want to stay cooped up in that house forever—" He caught Napstablook's hurt look and hopped to face him again. "But that's not because of you! It was all my fault! I just—I was tired of all the—I was just sick of—" He fumbled for the right words, not wanting his cousin to cry because of him. "Oh—FORGET IT!" Mad Dummy's head flailed around. "Come on, just PUNCH ME already! I know you want to!"

Napstablook timidly shook his head. "N…no...I would never..."

"I deserve to be punched! I may be a punching bag, but not even ALL the times I've been punched could compensate for what I've done!" Mad Dummy hollered, his head and torso flinging about. "I thought I was doing you a favor by staying out of your life, and I was wrong! You have every right to hate me, so just DO IT!"

Napstablook shut his eyes, holding out his little stub of an arm. He swatted at his cousin, but could only gently tap his head.

Mad Dummy simmered down and sighed, staring at the ground. "Napstablook...why are you always so...soft? I mean, I could've come to visit you at any time! I lived right next door to you all this time, for crying out loud! I could've came to comfort you after Hapsta left...but I didn't." He hung his head. "Why are you still here?"

"...I…I still need to get my CD back from Undyne..." Napstablook innocently replied.

"You know what I mean." Mad Dummy shook his head. "All this time, I always thought you favored Hap. Why can't you just forget about me!? Just...forget what I've done...?" He started shaking in rage again. "Honestly, I really wouldn't blame you if you at least tried to forget about me!"

Napstablook had even more tears in his eyes. "Y-you're my...family..." He whispered. "I love you both the same...it may show in different ways, but I always have..." He huddled close to his cousin to comfort him. "I can never hold a grudge...especially against my own family..."

Mad Dummy took a deep breath, tears evident in his eyes as well, but he forced them back. "Napstablook..." He began, trying to compose himself, "I…really don't deserve a cousin like you."

Napstablook let go and they were silent for a moment. The dummy looked up at him and smiled, surprising the ghost.

"Thank you..." Mad Dummy told him, although he cleared his throat after catching his smile, pretending nothing happened. "Er—at least we're together now, huh? And on the surface..." He looked around. "I never dreamed this would happen, but...it's pretty nice."

"It is..." Napstablook smiled, giving his cousin a hug.

Mad Dummy flinched, not used to this gesture, but gradually calmed down a bit. He looked down, noticing that Napstablook had tears in his eyes. "What, you're crying now!? Come on!" Mad Dummy rolled his eyes. "One day ya gotta learn to toughen up!"

"I'm just...so happy to see you again..." Napstablook said softly.

Mad Dummy's eyes widened as he awkwardly stood there, glancing around to make sure no one was watching. As time passed, however, he slowly leaned his head down, almost wishing he had arms to hug his cousin back. "I'm...happy to see you too," he mumbled.

The two were in such a content state, they didn't even pay attention to the thundering footsteps behind the front door.

"Hey, Napstablook? Here's your—"

Undyne kicked open the door to return the ghost's CD, but cut herself short when seeing the two cousins happily hug. Immensely confused, but not wanting to interrupt a heartwarming sight, Undyne slowly stepped back and smiled a little, returning inside.

"I'll...just wait for you."