Garret shook his head, "No permission, and it had to be outside the castle." He grinned his devilish grin once more, "Half the fun of it is in sneaking out, sooo..." his eyes took on the dangerous glint that suggested he was up to something wicked, "The Shrieking Shack is a good spot."

He realised that yes, they did have prefect friends... but to invite them, they'd have to do it sneakily. It would probably be easier to sneak around with prefects knowing about the whole deal anyway, considering they could help out with keeping the professors distracted, "The prefects can come, but only if they promise to keep it quiet."