You're wrong about River. River's not on the ship. They didn't want her here, but she couldn't make herself leave. So she melted... Melted away. They didn't know she could do that, but she did.
River ,'Objects In Space'
Previously 1: The Who Whating How With Huh?
Is it better the second time around? Or the third? Or tenth? This is the place to come when you have a burning desire to talk about an old episode that was just re-run. And keep it spoiler-free so the Un-Americans can play too.