u/NagitoKomaeda_987

For me, it's the titular Invader Zim himself.

When series creator Jhonen Vasquez was asked on Twitter if there are any queer characters in the show itself, he responded, "I don't even know that there are any straight characters on the show or characters that like ANY other kinds of characters" - heavily implying Zim himself (among many others) is AroAce. This can be seen in the show itself, with Zim showing visible distaste in the prospect of being in a relationship in "Tak: The Hideous New Girl" when he believes Tak (a female Irken) has a crush on him (in reality, though, she hates his guts). He participates only to monitor "human love rituals" and eventually tries to break off the "relationship" once he believes she is no longer useful to him.

Irkens also reproduce via gestating their young in glass tubes and lack any outwardly visible reproductive organs, so they may not have any at all, which would make Zim (and all other Irkens) asexual by default, so… yeah. But either way, I still headcanon Zim as AroAce no matter what.

For me, I feel more people know who Loona is than what Helluva Boss is.