Moony had his hands filled with books as he tried to unlock the door. He had his key out before he realized the door was unlocked. He pushed the door open and instantly smelled a mix of pot and sex and...peanut butter? If it wasn't so close to the new moon he probably would have been able to tell who was...doing things. He put the books down and would have gone straight to his room to avoid everything, but he heard voices in the kitchen and one of those voices was Emily.
He went to the kitchen and saw Sirius in his boxers and unbuttoned shirt basically rubbing on Emily.