Peter didn't realize that everyone wasn't going to be wearing costumes. He thought this was a "superhero" thing and therefore was supposed to dress in his costume. Secret identities and what not. He told his Aunt May that he was going to be out for the day, and told Jubilee that he was visiting Harry again. He had one of his Aunt May's cherry pies, however, and hoped that the other Teen Titans would like it. He sure did!
He came to the place that Hulkling had given him via text message and knocked on the door. Dressed in his costume, he was sort of a silly looking sight, actually. Spider-man waiting with a cherry pie in his hand, and a small plastic bag that had the pie cutter that his Aunt May insisted that he take. Shifting awkwardly, he waited and wondered when they were going to let him in.