I would love to hear your aro headcanons!!!!
Thank you for this ask! 💚💚💚💚💚
I'm focusing on It's Always Sunny but basically anything that I get invested in, I will always have at least one aro headcanon for.
IASIP can be remarkably aro-friendly. None of the main characters are in long-term romantic relationships (or, in Mac & Dennis' case, a traditional and easily labeled relationship). Their most important relationships are with each other and whether you see those relationships as platonic, familial, or romantic in some way, there is still a lot of relationship anarchy inherent to the show.
In terms of specific arospec headcanons for characters, arospec Charlie was my very first intro to the show as I saw an aro mutual post about it almost a decade ago.
I made a whole post about it back in June (specifically for a reading of lithromantic Charlie) but there is something so distinctly aro about how Charlie interacts with romance that you could tell me any arospec headcanon for this dude and I would probably agree.
I also love the reading of Dee as aromantic and allosexual. She frequently prioritizes sex over more traditional romantic activities (like in FvR where she'd rather have sex than go on a second date). She's also the rare female character on TV whose story doesn't revolve around romance and as she gets older and romance continues to not factor into her story, I just think that's really cool.
There's also this great quote from Kaitlin Olson on Dee's character from the Relationships BTS Sunny S5 promo:
Here's the thing about Dee and romance. If you're waiting for that to happen, I don't think you're watching the right show.
Finally, while I personally think this man will go unlabeled forever, I think it's really cool to view Dennis though an arospec lens. He hates Valentine's Day and people think he doesn't have feelings because he doesn't express or experience love in a traditional way. That's aro relatable as hell.
Also, he invokes the Split Attraction Model when describing his relationship with Mac to Mandy, that "he sleeps with women but is emotionally involved with Mac". While the SAM is not limited to the aspec community, it is still a very popular model within that community to distinguish between one's romantic and sexual orientation. I also find it notable that he specifically says "Mac" rather than "men" in general, which is interesting evidence for a demiromantic Dennis reading.
Also, as the gang is usually ignorant of these kind of things, I'd like to think that the only person who's heard of any of these terms is probably just Mac when he was making an effort to learn more about the queer community.