I wanted to make another character inspiration meme, and I went with Ivis and Ivin the eye-headed hydra. Now let's take a look to which characters they're quite related to those eyeball fellas.

Devon and Cornwall (Quest for Camelot)
Definitively the most related conjointed duo! Devon and Cornall are a two-headed dragon with a big body and different heads and they don't even get along with, just like Ivis and Ivin. Devon has a long and thin neck while Cornwall has a short but thick neck. Silly, right? If Ivis and Ivin have to meet a character related to them, it's definitively Devon and Cornwall. I'm even planning a commission about that!

Hydra (Hercules)
Ah yeah, that hydra from Hercules. Ok, it has one more head than Ivis and Ivin, but there's something in common between them; they're bipedial and they're armless. That hydra's heads might look terrifying, but still, nice body and legs if I say so.
Does anybody draw this hydra anymore? I don't think I saw feet stuffs of it.

Ord (Dragon Tales)
Ivis' and Ivin's body is referred to Ord, and the model proves it (and it really has nice feet!) as explained in the ref sheet. Some differences; no arms, no wings, no spikes and Ivis and Ivin has slightly bigger claws than Ord.

Shuma-Gorath (Marvel Comics / Doctor Strange)
Yeah, it's that alien eyeball villain from several Marvel comics, especially Doctor Strange, and he even appears as a playable character in some Marvel vs Capcom games. Despite being an eyeball, Shuma-Gorath can even talk, same goes for Ivis and Ivin!

CatDog (CatDog)
I got room for CatDog in case I need to link another conjointed duo that doesn't often get along well. I'll probably relate Ivis to Cat since he's probably a little smarter than Ivin (I'm still pending about it) while I'll relate Ivin to Dog.

Infrared Ivan (My Life as a Teenage Robot)
It's that minor antagonist which appears in My Life as a Teenage Robot episode called See No Evil. Infrared Ivan (aka Invisible Eyeball) is a giant eyeball which can only seen with infrared vision (not the case for Ivis an Ivin). Once again, he's an eyeball that can talk. Also, the way how he got defeated is so worth it; Jenny kicks dust at Ivan's eyeball, damaging his eyes, then Ivan try to grab eye drop, but accidently picks hot sauce, a branch and a magnifying glass. Yeah, so worth it.
Imagine if Ivis and Ivin can be defeated the same way...