If they exist in a weird world apart from all the things in our world, you can just say what celebrities/characters/cartoon characters they WOULD have a crush on.
Alicia thinks young Steven Seagal is cute. She used to spend a lot of time watching action movies with Kattar and his movies were always her favorite. To be honest she cared 0% about the plot of any of them. They also used to watch one of the old X-Men shows too, and her favorite superheroes were Rogue and Gambit. Her favorite superhero in general is Spiderman. She actually enjoyed watching the 'Spectacular Spiderman" series with Kattar during their teen years, and she really liked "Into the Spiderverse" too.
Kattar has had zero celebrity/character crushes, but if he had to choose one he thought was pretty, it would probably be in the realm of Georgie Diaz from "Stuck in the Middle." (He used to have to watch a lot of Disney Channel shows with Alicia, though he hated most of them.) He's only ever been attracted to Alicia, but he does find brown skin and dark hair pretty. His favorite superhero is probably Static Shock. He loves the TV show and has watched the whole thing through more than once. His favorite X-Man is probably Wolverine.
Jinwoo is obsessed with fairy tales. He doesn't like movies or TV shows, and he's never had a crush, human or not, but he found the princesses pretty. Tiana was the prettiest in his opinion, but his favorite story is Cinderella, so by default, she is his favorite princess.
Kimberly has probably had a lot of celebrity crushes, so just to limit it down to a few. She liked Corben Blue from High School Musical when she was younger, and in the realm of cartoons, she thought Yoon Arikawa from "Godzilla XP" and Kevin E. Levin from "Ben Ten" were cute. She's also a pretty big fan of Zac Efron and Korean idols like NUEST's JR, SKZ Bang Chan, and Seo Changbin. (yes, she knows they're not tall, but she still finds them handsome, though they're younger than her.) A favorite cartoon character would be hard for her to pick, but it's probably Kevin E. Levin.