Black hair. Black clothes. Looks like Lydia Deetz was a Goth girl before it was cool. But her Goth isn't just a clothing style; she's a depressed, alienated teenager who identifies more with the dead than the living—at least the living she's living with.
Home and Family
We first meet Lydia when she's carried into her new home wearing all black and holding a camera. She digs the house because there's a spider on the banister. Yeah, there's loads of teen angst going on here.
It's clear right away that Lydia doesn't exactly get along with her father and stepmother:
DELIA: I can't believe we're eating Cantonese. Is there no Szechwan up here?
LYDIA: Plan to have a stroke from the amount of MSG that's in this food.
DELIA: This is our first meal in this house, so why don't we all do our little private parts to make it a pleasant one?
CHARLES: Don't bait your mother, Pumpkin. Soon as we get settled, we'll build you a darkroom in the basement, okay?
LYDIA: My whole life is a darkroom. One big dark room.
DELIA: So you were miserable in New York City, and now you're going to be miserable out here in the sticks. At least someone's life hasn't been upheaved.
So Dad is kind of patronizing and the stepmom is sort of wicked and overly critical. To put it another way, Lydia knows what it feels like to be stuck in a house with these awful people. That's why she likes the Maitlands so much.
Death Becomes Her
As someone who spends most of her time brooding and thinking morbid thoughts, Lydia's not scared off by a couple of dead people in the attic. She's just plain curious. Plus, she's the only living person who can actually see the Maitlands at this point. According to the Handbook for the Recently Deceased, it's because she's "strange and unusual" herself.
Put that on your college application, girl.
Lydia loves the Maitlands. What's not to love? They're sweet, kind, interested in her, and dead. But Lydia's obsession with the dead does have a bit of a downside. She gets so sad and disgusted with her parents at one point that she decides to commit suicide so that she can join the Maitlands:
LYDIA: He told me that if I let him out he would take me to the other side to find you.
BARBARA: No, Lydia, we're dead.
LYDIA: I wanna be dead, too.
BARBARA: No! Lydia, being dead really doesn't make things any easier.
ADAM: Listen to her on this, Lydia. This is something we know a lot about.
Lydia's parents don't really seem to care about her. First, she tells them there are ghosts in the house and they ignore her or don't believe her. Then they demand she help them round up the ghosts as a money-making scheme, which completely ignores the fact that these ghosts are her friends.
Lydia Saves the Day
The Deetzes begin to have second thoughts about turning Winter River into a supernatural amusement park once they see the grisly results of Otho's séance. But Lydia's the only one who thinks quickly enough to help the Maitlands:
LYDIA: Where are you? Help them, please.
BEETLEJUICE: Sure, I can help them. But you gotta help me.
BEETLEJUICE: Look, I'm what you might call an illegal alien. I want out for good. In order for me to do that, hey, I gotta get married[…]
LYDIA: Okay, just help them.
LYDIA: Betelgeuse. Betelgeuse. Betelgeuse.
BEETLEJUICE: It's showtime!
Lydia's obviously not thrilled about this quid pro quo, but she's so desperate to help her friends that she'll really do anything. It's not until the Maitlands are safe that reality sets in. She's about to become Mrs. Betelgeuse. The ultimate mixed marriage.
Luckily, Adam and Barbara are able to step in and rescue her from this matrimonial nightmare. With Betelgeuse gone, Lydia and her family agree to live in the house with the Maitlands. Lydia dials back her Goth look by about 30% and everyone's happy.
Lydia finally has the attentive, loving parents she's always wanted in Adam and Barbara. Heck, even Lydia's actual parents seem to care more about what's going on with her (Charles knows she got an A on the math test, after all). Life is good. Or good enough.
Helping out the Maitlands is a huge developmental step for Lydia; it's the only time she thinks about anything other than herself and how miserable she's determined to be. Ironically, the Maitlands kind of bring her back into the land of the living.
In fact, Lydia is one of the few characters in the film who shows character development. The Maitlands don't; they're dead. Her parents and their friends are stereotypes, not characters. Betelgeuse is, well, Betelgeuse.
So is this really Lydia's story after all?