Harry and the others had a simple idea: do what they had done in their second year, knock Crabbe and Goyle out, then use Polyjuice Potion to turn into them and get inside.
But when they proposed the idea and went to discuss it with their friends, Cedric vetoed it.
"I honestly never imagined you'd done something like that." Learning that Harry and the others had already done it in their second year left Cedric torn between exasperation and amusement.
Yi Qianqian's eyes, on the other hand, lit up, and she declared that Harry and the others really knew how to have fun.
Cedric looked rather helplessly at Yi Qianqian, who was brimming with excitement and then lamented that she could not try it herself, before explaining to Harry and the others,
"Do you remember the break-in at the Common Room in fourth year? Oh, no, I mean your third year?"
"I remember. My godfather did it." Harry nodded, indicating that he was very familiar with that incident.
Back then, Sirius had slipped into the Gryffindor Common Room with Crookshanks's help, intending to kill Wormtail, who had turned into Scabbers the rat.
But Wormtail had already fled by then.
Looking back, Harry and Ron had concluded that Wormtail must have left when they obtained the Marauder's Map.
Wormtail knew about the Marauder's Map too; his name was even still listed among its creators. So he knew that if he stayed in the dormitory, Harry and the others would grow suspicious as soon as they saw his name.
Although Animagi were relatively rare, quite a few people knew about them. Most importantly, they were the subject of the first Transfiguration lesson in third year.
Well, Wormtail probably had not originally remembered the contents of the first third-year Transfiguration lesson.
But since