Omanyte are generally super shy, bonding with one requires FINDING them, but once you manage it, they'll stick to you like glue while staring lovingly at you 24/7
Omanyte doesn't have a domino mask at all even as a Pokémon. It's absolutely inspired by Splatoon- the ears are a hint as well. On the next page, Omnastar's "teeth" are also based on Inkling "teeth", so it's safe to say Kinkymation had Splatoon on the brain when making these two.