(AKA what I think various Tangled characters would dress up as for Halloween 😋)
Rapunzel: The girl from The Ring. For one thing it matches the Decay Incantation, but I also just think that Rapunzel would prefer to dress scary over dressing cute. She gets to be cute every other day of the year! She wants to be SCARY for once, damnit!
Eugene: He would love any kind of cheesy matching costumes. But if he can't match with Rapunzel or Lance (which has a 50% chance of breaking his heart), he'd dress up as a sexier version of other, normal Halloween costume. Nothing too crazy or revealing, but he's definitely prioritizing prettiness over spookiness.
Pascal: There is no way Rapunzel wouldn't dress him up. I think she'd dress him as a tiny version of whatever she's going as. (Also, Eugene would be so salty over his wife matching with her pet frog instead of him.)
Maximus: NOPE. Nuh-uh! That horse is NOT dressing up— at least not without a fight. It'd take the entire castle to wrangle him into even just a festively decorated saddle, and then he'd pout for the whole night.
Cassandra: You would have to force her into dressing up. She's way too busy (and proud) to wear a costume, but if she absolutely HAS TO then it'd be something that she can easily DIY— like using some of the castle guard's uniforms to make herself into a musketeer. Just something easy but that doesn't look cheap.
Varian: He is definitely the type to come up with a LOT of costume ideas. Mad scientist is an obvious one and so is a vampire (since there's quite a bit of fanart I've seen of him as one), but I could also totally imagine him as dressing up as someone he knows. Maybe him and his dad dress up as each other one year. Oh, and he's of course dressed up as Flynn Rider more than a few times.
Lance: Like I mentioned before, Lance and Eugene are the KINGS of matching costumes. You know those two-person horse costumes that you see in cartoons? That's them. I think Lance is more willing to do an individual costume than Eugene would be, though. Lance would probably dress up as something traditionally Halloweeny— like a skeleton or pirate— and then add his own twist on it. Instead of just a skeleton, he's a cowboy skeleton. Instead of just a pirate, he's a pirate on vacation.
Red/Catalina: While she and Angry matching would be adorable, I actually don't think Red would want to do that. She also wouldn't want to be a werewolf, because that'd just be too easy. She wants to be able to stand out. I could definitely imagine her going as something that's both cute and spooky, like a ghost princess, and asking Rapunzel to help her with the costume.
Angry/Kiera: Any kind of animal and/or magical creature. She prefers the cool ones, like a dragon, but she can be convinced to dress up as something cuter if she thinks it'll get her more candy. Lance obviously helps her make the costume, and if cameras existed, he would be taking dozens of pictures of the girls and sending them to everyone he knows.