Grab a seat, alien friends, we're watching anime. I like series across several genres so I'm sure I could find at least one we could watch together, and it would be a good way to introduce them to Earth culture and concepts*, and maybe even find some common ground!
*Okay, BIG depending on the anime here. I don't want to teach aliens that the best way to make friends on Earth is by punching each other while shouting about your personal ideals and convictions