X17 EXCLUSIVE - Ryan Phillippe Takes Amanda Seyfried As His Date To Kate Hudson's Halloween Party

And he looks pretty psyched about it! Wouldn't you be? This is Karen Smith we're talking about! Although she didn't go as "a mouse, duh!" - Amanda Seyfried went as a cute puppy!

But why was Ryan Phillippe trying to hide his mystery date on the ride over? Here's what our X17 photog on the scene had to say:

"Ryan and Amanda were definitely together but they didn't really want us photographers to see it. Before they realized we were around, they were laughing and chatting with other people at the party and were obviously a couple. Ryan was really sweet with her -- he had his hand on her lower back for a while when they were talking to another couple. They looked great together."

Who else kinda loves this match? I think they make a cute couple!