One common theme is chaos. Beetlejuice is a chaotic character, and when he crosses over into other universes, he often brings that chaos with him. For example, in crossovers with more orderly universes like 'Harry Potter', his presence disrupts the usual order of things at Hogwarts.
A third common theme is self - discovery. In some crossovers, like the one with 'Alice in Wonderland', Beetlejuice goes on a journey similar to Alice's. Through his interactions with the strange Wonderland characters, he learns more about himself and his own powers. This theme of personal growth within a crossover setting is quite popular in Beetlejuice crossover fanfiction.
Another theme is the clash of different aesthetics. Beetlejuice has his own very distinct spooky - comical look and attitude. When he crosses over with, say, a more serious horror - themed world, like 'The Conjuring' universe, the contrast between his more light - hearted spookiness and the intense horror creates an interesting dynamic.
I'm not really in favor of promoting hurt themes, but generally, if there are such fanfictions, they might include themes like Beetlejuice being ostracized or physically harmed by the living humans in the story. However, these are not positive themes and can be quite dark.
Another theme is growth. In many 'beetlejuice platonic fanfic', Beetlejuice or his friends in the story grow as characters through their platonic interactions. For example, Beetlejuice might learn to be more empathetic through his newfound friendship. It's a way to explore his character development outside of romantic relationships.
A major theme is self - discovery. When in a 'bottom' role, Beetlejuice has to re - evaluate who he is and his place in the world. Also, there are often themes of acceptance. He has to accept his new position and the way others see him. In some fanfics, there's also a theme of redemption. He might be trying to make up for past wrongs while in this more submissive role.
A theme that often pops up is self - discovery. Lydia, through her interactions with Beetlejuice, discovers more about herself, her own power, and her place in the world. Also, the theme of acceptance is there. Beetlejuice, who is often ostracized, finds acceptance from Lydia, and vice versa.
One common theme could be self - discovery. Since she is Beetlejuice's daughter, she might be trying to figure out who she really is. Another theme could be family drama. Given Beetlejuice's character, there would surely be some interesting family dynamics at play. And of course, the theme of the supernatural would be prominent as they are part of that world.
A prevalent theme is often her struggle with identity. Since she's Beetlejuice's daughter, she might not fit in either in the human world or the afterlife world completely. This can lead to stories about her finding her place. Also, themes of friendship are common. She could make friends with other supernatural beings or humans who are somehow connected to the Beetlejuice universe and they go through different experiences together.
The theme of transformation is common in Beetlejuice x Lydia fanfic. Lydia transforms from a normal girl (well, as normal as she can be) into someone more in tune with the spirit world because of Beetlejuice. And Beetlejuice also changes in a way, as he starts to care more about Lydia. This transformation theme adds a lot of depth to their relationship in the fanfics.
One common theme is adventure. Since the Valerian universe is full of exciting and unknown elements, when crossed with other universes, it often leads to epic adventures. For example, a crossover with a space - opera like Star Trek could result in a story where Valerian and his companions explore new galaxies together with the Star Trek crew.
One common theme is the clash of different powers. For example, when the Incredibles cross with other superhero groups, there's always the exploration of how their powers compare and contrast.
Power struggle is a common theme. Starscream is often power - hungry in the original Transformers series, and in crossovers, this trait is magnified when he enters new universes with different power hierarchies. For example, in a crossover with the Lord of the Rings, he might try to claim the One Ring to gain ultimate power.