This is based off a dream I had a while back where Rigby was dreaming that Mordecai looked like Frankenstein before Mordecai shook him awake. I added most of this to make it better. Hope you like it!
Rigby walked around the park house looking for his friend.
"Mordecai! Where are you, dude?" he shouted.
After being given no reply, he sighed and made his way to the last room he hadn't checked: his and Mordecai's bedroom.
"If he isn't in here I don't know where on earth he is," Rigby muttered to himself.
He walked in and found the room empty.
"Figures.." Rigby walked over to the window to see if he could catch a glimpse of Mordecai roaming around.
He suddenly heard the door slam and turned around.
"Hey, Mordecai-" Rigby instantly stopped speaking as he looked at his friend.
Mordecai looked like Frankenstein except for the fact that his face was still blue.
His hair was black and he had stitches all along the top of his forehead.
Rigby started at him wondering what had happened.
"Dude, why do you have stitches? And why is your hair black?"
Mordecai gave no reply as he stepped toward Rigby.
"Dude?" Rigby said as his friend was getting closer.
"M-Mordecai? What's wrong with you? You're freaking me out, man!"
Rigby started trembling as his friend backed him up against the wall and pressed his hands to the wall to prevent any escape.
Mordecai chuckled darkly as he removed one hand from the wall to tilt the raccoon's chin up.
He felt the raccoon flinch as he looked in his eyes.
"You're the one who did this to me, Rigby. You're the reason for what's going to happen to me," he replied with a smirk on his face.
"What do you mean? W-what's going to happen?" Rigby asked hesitantly as Mordecai's smirk turned into a glare.
"This." Blood started dripping from the stitches on Mordecai's forehead.
Rigby's eyes widened as he tried to pull away from the firm grip.
"L-let me go, Mordecai! Let me go!"
Mordecai gave one last smirk as blood poured and splattered onto the floor.
"This is all your fault."
"Rigby! Wake up!" Mordecai said as he shook the raccoon.
Rigby shot up, trembling and panting as he looked around.
He was in his room and Mordecai was kneeling by his trampoline.
It was just a dream, it was just a dream. Calm down.
He tried to control his breathing as Mordecai looked at him with concern in his eyes.
"You okay, Rigby? You look like that nightmare really got to you."
Rigby took a deep breath as he avoided looking in Mordecai's eyes.
"Y-yeah, you can go back to bed. It was just a silly dream."
Mordecai frowned as he observed Rigby.
"You don't look okay. You're trembling and you were screaming and thrashing in your sleep, dude."
Dang, he's onto me.
Rigby drew in a shaky breath as he finally met Mordecai's eyes.
"Alright, I'm not okay. But seriously, you don't need to stay up worrying about me. Go back to bed."
Mordecai sighed. "I have a right to worry about you, Rigby. Look at you, you're still trembling!"
Rigby glared at Mordecai. "So what? I'll stop trembling soon. Good night!"
Rigby started to lie back down only for Mordecai to grab his arm and pull him to a sitting position.
"Rigby, you're not going back to sleep until you've calmed down. I don't want you to be thinking about that dream only to go back into it."
"Why are you so caring all of a sudden? I've had plenty of bad dreams and only now are you caring so much!"
Mordecai's stern expression turned soft.
"You're my best friend, Rigby. I know you and I can tell that this dream was one of the worst ones you've had."
Rigby opened his mouth to retaliate only to be silenced.
"Don't tell me you're fine, dude. You're still trembling and I just want to help you. Won't you let me help?"
"Fine," Rigby grumbled as Mordecai's face lit up.
"Alright, anything you want me to do?"
Rigby shrugged as he trembled. "I don't know."
"Hmm..." Mordecai thought for a minute until an idea popped in his head.
He got off the floor and sat on the edge of Rigby's trampoline.
"Uh, what are you doing?" Rigby asked nervously.
Mordecai just ignored Rigby as he started to rub Rigby's back gently.
Rigby relaxed as Mordecai rubbed his back and he scooted closer to where he was pressed against the avian's side.
"Rigby, I want you to know that if you ever have one of these dreams again, a bad one that just happens every now and then, you can talk to me, okay?"
Rigby nodded as Mordecai started to massage his shoulders tenderly.
After a few minutes, Mordecai heard Rigby speak softly.
"Thanks, Mordecai," Rigby said before drifting to sleep.
Mordecai smiled as he gently lay Rigby back down.
"Anytime, dude."