Sulu knew that this was one of those Terrible, Horrible, Rotten, No Good ideas that he was occasionally prone to having. He was grounded, after all; inviting Ianto over to prove that he wasn't just making up the things he'd been talking about was kind of pointless if you couldn't get to the car to prove any of it.
Still, he'd heard his parents leave to visit his aunt in Bakersfield, so... why not? It wasn't like they'd notice - he was really good at hiding his tracks. So, he'd invited Ianto out to prove that his universe really was all he'd said it was. It was the least he could do to prove he was seriously as awesome as he made himself out to be, after all. So, he waited in his room for the inevitable worldhopping Ianto Jones, wondering if that was too specific a place but figuring that worldhopping itself was already pretty specific an art.