Dawson Casting: Lydia...maybe. Her age is never stated but Winona Ryder was 17 when the movie was filmed and the character is referred to as a little girl So it's possible the character is suppose to be about 12-14.
Mid Development Genre Shift: In the original script, the film was imagined to be more like a graphic horror film rather than a comedy, and instead of marrying Lydia, Betelgeuse was originally going to rape her.
Name's the Same: Funnily enough, there is a red giant star named Betelgeuse, and yes, it's pronounced the same way.
Throw It In: 90% of Michael Keaton's lines are ad-libbed.
Vaporware: The scrapped sequel Beetlejuice Goes Hawaiian. Apparently, Burton deliberately came up with a ridiculous premise in order to stop the sequel from being made. Kevin Smith was offerred to do a rewrite of the script before being attached to the also-unmade Superman Lives. His response to the execs boiled down to "Didn't we say all we needed to say with the first Beetlejuice? Must we go tropical?"
What Could Have Been: Originally, the movie was to have Lydia be a minor character and was to be your typical movie teenager. She would also have a sister named Cathy who befriends the Maitlands. Somewhere along the planning process, Tim Burton decided to take character traits from both and make Lydia a Composite Character.
Likewise, Betelgeuse himself was a lot more sinister. Oh, and he had something along the lines of a Good Twin named Swallowtail.
Though it was with a different name, that plot point was eventually used in the animated adaption.
Also, originally, Tim Burton wanted Sammy Davis Jr. to play the role of Betelgeuse.
Wes Craven was the first choice to direct before Tim Burton got involved.
Originally it was going to be mentioned that Beetlejuice committed suicide when he hung himself over a woman when he was drunk - and that he botched the job and ended up suffocating painfully instead of a quick snapped neck. There wasn't time for it.
Screwed by the Network: Subverted in real life, as both ABC and Fox Kids aired this show simultaneously in the 1991-92 season (FOX aired it on weekdays and ABC aired it on weekends), making it the first Saturday morning cartoon to do so. The show's end in 1992 is normal, as most cartoons based on popular movies don't last very long (The Real Ghostbusters, The Mask: The Animated Series, and Ace Ventura: The Animated Series are the only exceptions). On the show, some of the episodes were thin metaphors about Executive Meddling and Moral Guardians trying to make Beetlejuice's life (aka the show) Lighter and Softer for audiences.
Fox's first-run of the show was very scattered, running all new episodes for the first month, then throwing in repeats up until November when it went into all repeats until February 1992. New episodes plus repeats aired through February sweeps, then the final four new episodes aired the first week of May.