I think HP is the start of fandom; you get into it and next thing you know you're in several other fandoms. Everyone loves HP; haters are instantly jumped if they make a derogatory comment about the books or movies.
Dame Maggie Smith "The last couple of years have been a write-off, though I’m beginning to feel like a person now,” she said. “My energy is coming back. S*** happens. I ought to pull myself together a bit.” Harry Potter