Regulus/Theo
Regulus couldn't believe that he was voluntarily going to a party wit Gryffindors. This was nothing like the parties he was used to. There were no elegant robes, no classical music, no traditional dances. In fact dancing looked a lot like jumping in place. This was not what he liked.
He scanned the room for signs of people who wouldn't appreciate the jumping around. There wasn't anyone he knew but there was another slytherin.
"You are Theo, right?" he said as he got something to drink (not alcoholic, because he had his limit with some wine with dinner). "Regulus Black," he added, although everyone knew every name. Introductions were still good manners. "How are you enjoying this new world?"