Only Britney, Oops the song and video are very much remembered in pop music. Nobody even remembers GaGa's atrocious video for BTW and Katy looks great and I love E.T. just not iconic.
Maybe you should use your common sense a little more. When people think of an alien, they expect a bit more than one that looks exactly like a human being. That's why nobody remembers Britney the alien except her stans.
I'm not saying Britney's song and video aren't iconic, cause it clearly is. But her alien persona/look is not iconic, at least to me. And clearly to a few others too.
Lemme call NASA and send y'all Katy stans' asses to Mars cause we don't need the Curiosity Rover anymore. Explore, breathe and live in Mars, sis. Y'all probably don't even know Clark Kent/Superman is actually an alien. Mess.