If you watch the first episode of a series with someone, you've formed a certain non-verbal contract to keep watching it with them. You can't skip ahead or sneak in an episode while they're away. Match up your schedules, stay in sync, discuss. Unless they don't know. It wouldn't hurt... just to watch one episode. You can watch it again with them later and pretend it's new for you. How could they ever find out? It's not cheating!