I'd like - inviting aliens and have them observe what we do because so much of what we do that we take for granted will just be weird or extraordinary or just plain dumb when observed by an alien from another civilization.
Grab something off the shelf that's on the spaceship-an ashtray, it doesn't matter what. Because I can tell you, if they flew here from another galaxy, no matter what you've pulled off the shelf, it'll be unlike anything we have on Earth.
After 50 years of television, there's no other conclusion the aliens could draw, but that most humans are neurotic, death-hungry, dysfunctional idiots.
Perhaps we've never been visited by aliens because they have looked upon Earth and decided there's no sign of intelligent life.