Crab Monsters

A few games in the Castlevania series have included crab-like enemies; three different types have appeared so far. They were first introduced in the non-canonical games Akumajō Special: Boku Dracula-kun and Kid Dracula, where they appeared as cute little robots resembling crabs. They later appeared as bizarre crawling skull monstrosities in Rondo of Blood, to finally appear as a menacing giant crab boss in Order of Ecclesia.

All of these enemies, even if they belong to different series, have used bubbles as one of their forms of attack.

Akumajō Special: Boku Dracula-kun / Kid Dracula
Boku Dracula-kun and Kid Dracula were the first to introduce crab-like enemies, where they appeared as robot crabs that crawled in between indentations of metallic walls.

Castlevania: Rondo of Blood
In Rondo of Blood, the rather disturbing Skull Crab made its debut into the series. It was a crawling skull consisting of a skull with legs made of bones. It crawled along the ground and emitted foamy bubbles to attack, or eventually lashed out with its rather long and pointy tongue.

Castlevania: Order of Ecclesia
Brachyura, a giant crab which could scale among the walls of the Lighthouse, appeared as Order of Ecclesia's third boss.