If Sirius Black was innocent, why was he standing in the middle of a street laughing like a maniac next to the bodies of twelve murdered Muggles? It has always been one of the biggest pieces of evidence against him. Some people say it was a trauma response. Others think he was laughing because he believed Peter Pettigrew had blown himself up. But there’s a tiny detail in Prisoner of Azkaban that makes me think there’s another explanation. Earlier in the book, Professor Flitwick teaches the students the Cheering Charm. Harry slightly overdoes it on Ron, and Ron ends up in fits of hysterical laughter. He has to be taken away for an entire hour before he’s able to perform the charm himself. The spell was powerful enough to completely incapacitate him. Now remember what McGonagall says about Pettigrew. He hero-worshipped Sirius and James, but he was never in their league talent-wise. So if Pettigrew knew he couldn't beat Sirius in a duel, why would he try? He could use something else. What if the Cheering Charm is how Pettigrew incapacitated Sirius? Think about the sequence. Pettigrew uses the charm on Sirius, leaving him helpless and laughing uncontrollably. He then blows up the street, kills the Muggles, transforms into a rat, cuts off his own finger and escapes. And when Fudge arrives, he says Black was still laughing. If Sirius was simply reacting to the explosion or suffering a trauma response, would he really still be standing there laughing by the time the Ministry arrived? What if Sirius wasn't laughing because he was guilty? What if Pettigrew made him laugh? The Cheering Charm might explain the single strangest detail of Sirius Black's entire arrest.