Sirius was afraid of spiders, and Remus knew it. All of the marauders did. Every once in a while, a spider would turn up, and being the good boyfriend that he was, Remus would get called upon by Sirius to take care of it. One night, Remus was helping a professor with something, and there was a spider on Sirius' bed, but Remus wasn't there to save him. The other two marauders, James and Peter, had gone somewhere with Lily, but Sirius had opted to wait up for Remus in hopes of getting a good snog when he got back. Sirius didn't know what to do, and he just screamed and eventually just broke down and cried because he was so scared of a little spider.

Remus came back to the dorm and heard sobs coming from inside. He burst through the door and found Sirius crouched on top of a trunk, avoiding a tiny spider, and crying his eyes out. When he heard the door open, he leapt at Remus and started screaming.
"Remmy! Please kill that horrid thing!" Sirius was hysterical, and Remus calmly picked up the spider and put it outside the window.
"Siri, you're okay. It was just a spider. Don't worry. It can't hurt you. I love you." Sirius buried his head in Remus' chest and one last sob came from his lips before his entire body relaxed.
"I'm sorry, Remmy. I don't know why I did that." Sirius kept his head in Remus' chest from embarrassment.
"Siri. You are fine. I don't care that you got scared. It's okay to be scared. You've seen me a lot worse than this before." Remus meant it completely, and it was very true. "C'mon Siri. Let's go to bed. You can sleep with me if you'd like." Remus offered.
"Oh, yes please." Sirius answered him with tears still in his eyes. Remus helped Sirius to his feet and led him carefully to the bed where Sirius snuggled up to Remus and fell asleep soon after. Remus was soon to follow, and they woke up to the sound of morning rain on the windows.

I thought this was cute! I was thinking about who would be scared of spiders between the two of them, and it was definitely Sirius. I hope you liked it too! Thanks for reading!