This alien is incredibly well-behaved around children, and equally as timid/innocent. E.T. is something the children instinctively embrace, whereas all the adults only seek to capture it and shut it down; in that way, E.T. makes a metaphor for imagination and bewonderment in general. The metaphor was much more potent when you saw police officers armed with shotguns as Elliot tries to elude them on bicycle (which were replaced digitally with walkie talkies when the movie was "re-released" in 2002 on DVD, and then rightfully returned when the movie found its way to Blu Ray).
These aliens would be amazing if they were aggressive enough to actually invade Earth (if they could get a ride from Endor); it'd be like a bunch of teddy bears demanding to be treated as equals, and not as a cute plush toy to toss on the bed of every 5-year-old girl. But these little furries are, in actuality, packed with fury--just see how their tribe single-handedly brought down several AT-STs, and a platoon of laser rifle-equipped Storm Troopers. Making a sort of allegory to the Vietnam War--in the truest sense of guerilla warfare--they were armed with the advantage of being familiar with their surroundings, as well as some spears and rocks.
These aliens are a completely cliched stereotype of what aliens look or behave like--then again they are only vending machine prizes in an arcade ("Pizza Planet")--little green men with antennae, three eyes, and uniforms, who say "take me to your leader." They are easily impressed, and hold as their god "the Claw," a taloned- embodiment of a sort of natural selection.
They burp, smoke, drink coffee and booze, and are completely mysogynistic--traits which make these "worms" incredibly human-like. Each is equipped with its own personality and enough charm to make you forget it has more than one pair of arms. It seems all the aliens in the Men In Black franchise fit this kind of description--a physical likeness to a kind of insect or annelid, with the behavioral likeness to a human being, for better or for worse.
He looks more like a dog than an alien, which is exactly why he is taken to an animal shelter when he gets knocked-out by a truck after he arrives on Planet Earth, and is subsequently adopted by Lilo. Little does she know he is a weaponized alien experiment from outerspace, endowed with super-human strength, in addition to a heart that is as fuzzy and warm as he is.
Dressed like a Viking, it makes sense that this faceless little Loony Tune with an undeniable Napoleon complex be so bent on conquering the universe. Marvin is equipped with all the technology we imagine all aliens must possess--giant, intricate computers and disintegrating pistols--as well as a dog in a helmet, which also seems to occur naturally in outer space. This is an outerspace vision only plausible in the world of Duck Dodgers.
Seth Rogen is Paul, and consequently, Paul is Seth Rogen. That fact makes Paul, consequently, the same kind of pudgey-lovable stoner character Rogen inherently portrays in his films. The film, made by and starring the same guys behind Shaun of the Dead and Hot Fuzz, is a parody of UFO-geek culture, complete with all the expected gags and cliched tropes (e.g. the typical "hide-the-alien-from-the-governement story), and Paul becomes just a vehicle for laughs, riffing off of every far-fetched and unfound Area 51 alien claim stemming back to the fifties (with the appearance to match).
This sitcom-ready alien has a great sense of humor, and a voracious appetite for housecats, on which his diet is heavily based. He crash lands into just the right household, a family willing to hide him from the government and nosy neighbors, even at the cost of their own sense of normalcy. ALF, the last of his kind (his home planet was destroyed), does learn the ways of Earth, but he never truly stops being one of a kind. The show aired from 1986 to 1990.
Their heads are essentially skulls with giant brains, something that sounds frightening until you see one (or 100) of these guys in Tim Burton's crap-terpiece Mars Attacks! in which he experimented (unsuccessfully) with some early CGI-technology. The concept also sounds neat on paper, retro H.G. Wellsian alien invasion motifs with little hellbent men bent on taking over a planet much bigger than themselves. It just didn't gel correctly, and feels like Tim Burton was needing the spare change, although these little guys are incredibly amusing in how they talk, fail to intimidate, and especially how old-timey music causes their brains to explode inside their glass fishbowl-style space-helmets.
In a movie full of blantent product placements (i.e. that WTF-inducing MacDonalds dance party scene), puppetwork that would make Jim Henson cringe, and unyieldingly corny acting performances, Mac was a force of good (even if he does come off as a poor man's E.T.)--after all, he saved that boy in the wheelchair from drowning after he plummeted off a cliff into a underlying body of water. The only thing he can't help is the fact that he's trapped in such a god-awful movie.