Sirius is dating Marlene. He loves her. His dick just also loves basically the entire school. Unfortunately like most teenage boys, his brain is his dick. Therefore, he is Not Faithful.

Marlene finds out one day after he came onto the wrong girl and she told Marlene. She is Pissed. She's pissed but she's not just gonna tell him and yell.

Instead she waits for him to come back to the common room when it's full.

"Can I have your attention!" She yells. She gets it. All of Gryffindor looks at her as she pulls Sirius on top of a table next to her. She offers him a smile. "Star, I found a really wonderful spell that I want to share with you that I think everyone should see."

"Uh-,"

"Ready, love?"

"Marls, what-,"

"This is a spell that will truly highlight something... significant about Sirius. Something he's put a lot of effort into, so he must be proud of it, right? Well, it'll bring that into view for all of us."

And then she points her wand at him, and she casts. She casts the anti-cheating spell. It's only made for quills, of course, and it's never been used on a person before.

When the spell is used on quills, and the user cheats, their quill lights up a very bright purple. It is easy to spot, and can even be seen through quill covers made of thick material.

Marlene hadn't expected it to do anything. Truly, she hadn't.

But it did.

The spell took effect immediately. It washed over him and as it did so, his dick lit up bright purple. It was clearly visible through his boxers and trousers, so much so that elder students covered the eyes of younger students.

As Sirius took in the situation and stared at her in horror, some students began laughing. Quite a few, actually.

They laughed, but Marlene simply stared at him, extremely satisfied.

"Marlene! How did- I didn't mean to-,"

"Shove it, Black," she snapped. "Let's hope this'll keep you from cheating on your next girlfriend."

And then she jumped down from the table and with Lily at her side, they stormed up to their dorm together, leaving him standing on the table, his purple, cheating dick still visible to everyone around him.

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