Well there are some things you might not know about him! A major "oops" in the film department. Or Spielberg got onto Lucas' shit list.
From Cracked.com: [brackets, formatting and captions mine]
E.T. is a Sith Lord!
E.T. is the charming story of an alien who looks like your grandfather's swollen testicle arriving on a hostile alien planet and refusing to wear pants while hanging out with a small child. But, at least he was harmless, right? Yeah, except for the little fact that he was a goddamn Sith Lord.
Why It's Not That Crazy:
We know members of E.T.'s species exist in the Star Wars universe because we see them in the Galactic Senate during Star Wars: Episode I - The Phantom Menace, assuming you can bring yourself to watch it again and have enough money in the scotch budget.
This is the Galactic Senate! Now put some bloody clothes on.
When E.T. sees a kid in a Yoda Halloween costume he gets excited, as if he recognizes Yoda from, say, the Senate (as to why a kid would be wearing a Yoda costume if Yoda was a real creature from another galaxy, we'll get to that in the next entry [concerning Han Solo and Indiana Jones—except this could be E.T.'s dream!]).
E.T.: I didn’t know Yoda could be found in a dreary subdivision filled with builders’ Stockbrokers’ Tudor houses.
“Home, home, home! Home, home, home!”
E.T.: It’s Yoda, all right…
We also know that he has powers suspiciously similar to those displayed by Force users -- such as levitation ...
... and healing.
But, E.T. also demonstrates one power that goes way beyond what a goody two-shoes Jedi can do -- he brings a flower back from the dead and later revives himself.
Both a potted plant and E.T. himself are risen indeed!
Jedi can only kind of make like Casper and haunt their students, but [Chancellor Palpatine / Darth Sidious in] Star Wars: Episode III - Revenge Of The Sith told us that at least one Sith mastered death.
So, E.T. is from the Star Wars universe and demonstrates a power that only the Sith have, making our conclusion foregone. He must be an extremely powerful Sith, too, albeit one that's [been] severely weakened by his time on Earth. You can leave it to yourself to determine what he was doing on our planet, but E.T. has a very different tone when you consider that, rather than helping a kindly lost spacefarer home, Elliot was actually helping a Sith Lord get back to murdering the galaxy.
Now we know what E. T. is really like!