Seth, walked in dressed as his favorite fairy tale character...
the Mad Hatter. From his favorite Brother's Grimm tale,
Alice In Wonderland. He wasn't too familiar with much muggle stuff, but that book was one introduced by his mother.
He approached the table and grabbed a sticker paper, to write down his name:
Seth smiled at his name tag and pressed it on his, visible enough for people to see.
................
John, walked in accompanied by his 'brother-from-another-mother.' He hadn't been at Hogwarts since he graduated two years ago. Dressed as his favorite character, from his all-time favorite comic book Captain America. He walked up to the table and grabbed a name tag:
He pressed it on his costume and smiled. He felt like a child, at an amusement park! xD