They wear red French-style berets, which, combined with their species, seems to be a reference to French dishes such as escargot which use snails as a main ingredient. This, combined with the name of the local boss, Mollusque-Lanceur, give Bubblaine a subtle French theme. The males have moustaches, brown shell necklaces, brown bodies, and white shells, and the females have eyelashes, pearl necklaces, pink bodies, and light tan shells.
Bubblainians are skittish creatures, as when Mario approaches them after having captured an enemy, they will duck into their shells and yell for him to go away. This may in turn be a reference to the "cowardly French" stereotype.
Super Mario Odyssey
Bowser invades their kingdom to steal their beloved Sparkle Water for his wedding with Princess Peach.
At the game's finale, in the Moon Kingdom, a few Bubblainians can be found in attendance of the wedding between Bowser and Princess Peach. Like other attending members, they were brought forcefully. After beating the game, they can be found at the entrance of the Moon Kingdom near the Odyssey, and in the start of Darker Side.