If Harry Potter goes to Hotel Transylvania in fanfiction, he could find himself in a series of comical and adventurous situations. He may accidentally use a spell that turns one of the monsters into something unexpected. He'd be intrigued by the hotel's unique architecture and the way it's hidden from the human world. He would also be faced with the challenge of adapting to the different rules of this new place. For instance, the way magic is used or not used in Hotel Transylvania might be different from what he's used to at Hogwarts.
Well, he might be really confused at first. The magical world he knows from Hogwarts is quite different from the spooky yet fun world of Hotel Transylvania. Maybe he'd try to use his magic wand to do normal things like open doors, but the doors in the hotel work in their own strange ways. He could also meet all the unique monsters and have to learn their customs and cultures, which would be a whole new experience for him.
In the fanfiction, Harry Potter could become friends with some of the characters in Hotel Transylvania. For example, he might bond with Dracula over their shared experience of leading a group of magical beings. He could also introduce some of his Hogwarts magic to the monsters, like showing them how to play Quidditch. But he would also have to deal with the fact that he's in a very different kind of magical place, and some of his usual spells might not work as expected.