This SCP is a dance. The name of the dance is going to be "The Perlacha" because I think that sounds catchy and delicous, but in the article, it would be "The ████████" because reasons.
The SCP has a chance of taking effect whenever a group at least 7 people are dancing to a song who's title and singer's name both begin with a "P".
(I could change this, because this is kind of a stupid way for an SCP to take effect, but it's just a starting idea.)
The initial group of people will find it impossible to stop dancing The Perlacha once they start. This isn't a compulsion. If any person sees the group of people dancing, they will join in. Again, this isn't a compulsion. For some reason, the person will always take the dance as a kind of threat, and always come to the conclusion that joining in on the dance will serve as a kind of peace offering.
Anyone who joins in on the dance will also be unable to stop. Once the group of dancers reaches a certain number, (I'm thinking something a little over 100) they will all express hostility to anyone outside their dance group, and attack them with powerful limb movements involved in the dance. Now you have a group of 100 people that are dancing other people to death, and you don't know what to do.
What do you think? Any and all critcism is welcome, because I genuinely love this idea, and I really want this to become a mainlist SCP, because I think it could work.
Edit: Thanks, moogoescow. I too find an army of dance warriors quite funny.