Cast the Expert: The doctors are real doctors. Spielberg mentioned that this was necessary as they would be better at rapidly spitting out terminology that required years of medical school to lean than any actor who'd been simply given a briefing on it. Humorously, this lead to some competition amongst local doctors who all wanted to be in the movie.
Colbert Bump: Sales of Reese's Pieces candy skyrocketed after their inclusion in the film.
Cross-Dressing Voices: Played straight with E.T. in the original version and in the Japanese dub, but averted in the Mexican Spanish dub.
Harrison Ford filmed a scene as the principal of Elliot's school, set after he frees the frogs, which Spielberg cut because he felt Ford's presence was too distracting.
Two deleted scenes were reinstated for the 20th Anniversary Elliot shows E.T. the bathroom and gets a call from his mother. E.T. plays around in the bathtub, which Elliot thinks he's drowning. Turns out he was having fun. The other one shows Mary finding Mike and Gertie during trick or treating, Gertie spills the beans on where Elliot is, and she tells them to get in the car.
There was a subplot cut where E.T. was in love with Elliot's mom. He goes into her room and leaves a Reese's Pieces on her pillow.
There's a scene of when E.T.'s getting Elliot drunk. Elliot gets sent to the nurse's office and writes the plans for the communicator on the wall.
There was originally an alternate ending showing the boys playingDungeons & Dragons with Elliot as the dungeon master. The camera pans up to the roof, where the communicator is calling out to E.T.
Enforced Method Acting: Filmed in chronological order so that the cast could become genuinely attached to the E.T. character. Young Drew Barrymore, in particular, took it the hardest: she was genuinely frightened when she walked in on Eliot with E.T. in his room and in tears during his Disney Death scene.
E.T. was voiced by the late voice actress Kazue Takahashi in the first dubbed version and the second dubbed version, he's voiced by both Ako Mayama and Rica Matsumoto at the same time (who, by sheer coincidence, they will reunite together again, except this time as enemies, as Aguila Setme and Lilcarla Borgnine respectively.
Gertie's line "I don't like his feet" was adlibbed, as was her "Give me a break" response to the claim that grown-ups can't see ET.
When Elliott yells "It was nothing like that, penis breath" Dee Wallace was supposed to angrily yell at him to sit down. When she actually heard him say the line, she starting laughing and they left that take in the movie.
Averted nicely unlike a lot of 80s movies. You can tell it was filmed in the 1980s due to the cars, the TV, and the family owning an Atari 2600 but it doesn't stick out like other examples. Many of the pop culture references they make like Star Wars or The Twilight Zone are still known by today's audiences.
On the other hand, jock older brother Michael's introduction has him playing Dungeons & Dragons without hinting at him having any geeky or creative Hidden Depths, which firmly grounds the film in the early 80s (the height of D&D's popularity as a fad) for fans of the film who are roleplayers.
The first choice to play Gertie? Juliette Lewis. Her father made her turn down the role and Barrymore was cast instead.
Shelley Long was approached to play Elliot's mother. She turned it down as she was already signed on for the comedy Night Shift.
Stan Winston turned down the opportunity to work on E.T.. He would regret doing so.
The book "E.T. from Concept to Classic" features many plot points and scenes cut from the script. One subplot from an early draft was to have a rival to Elliott named Lance who wanted to expose E.T.. The spaceship was going to land in a parking lot, but it was changed to a forest because that sounded more magical, amongst many others.
There was almost a sequel where an evil group of E.T.'s people come to Earth looking for him and torture Elliott and his family for information.
Corey Feldman was originally up for a role as a rival to Elliott, a dork named Lance who threatened to expose E.T. The character is in the book adaptation, but was cut from the script. Steven Spielberg promised him a role in a future film, and he would go onto be in Gremlins.
Originally E.T. was going to develop a crush on Elliott's mother. Some scenes of this were filmed before it was scrapped. It did make it into the novelization.
Michael was originally going to lure E.T. into his house using M&M's, but this proposal of Product Placement was rejected by the company's executive, who perceived the movie as having an Audience-Alienating Premise. Instead, Reese's Pieces were used, and the company that manufactured them sold so many Reese's Pieces that they were able to become a major competitor to the company behind M&M's. M&M's are still used in the novelization.
Christmas Rushed: An infamous example. "Hey Scott, make something awesome! You've got six weeks."
Creator Killer: This game is often credited for the Great Crash of 1983, which annihilated Atari and Warner Bros.'s value. While it didn't singlehandedly cause the Crash, it didn't exactly help matters, either. Atari boss Ray Kassar, who had already driven away several programmers that then founded Activision and demanded the game's short development timetable, was ousted from his position and he has not been affiliated with the entertainment world at all since 1983. Shortly afterward, Warner sold off Atari, and the classic developer completely lost all of its dominance when Nintendo, who broke off their attempted relationship and became a brand-new Arch-Enemy, released the NES and ended the crash in 1985, but they were able to hang around for another decade until Atari's inability to recover from the crash culminated in the Atari Jaguar, which finished off the studio.
Franchise Killer: In addition to being one of the ultimate Genre Killers in entertainment as far as video games go, this game also severely affected the status of Spielberg's classic film, and the E.T video game is rumored to be the reason why it took MCA/Universal another 6 years before they released E.T. on home video (it got a later reissue in theaters instead).
Genre-Killer: E.T is the mascot of the Great Crash of 1983, which not only reduced Atari to a shadow of it's former self for the remainder of the 80s and 90s, but destroyed almost everyone else in the industry, and likely would have sent gaming into a permanent small niche or worse had Nintendo not stepped up.