Blue Lava Bubble

Blue Lava Bubbles appear as enemies in three 3D Mario games, being the Super Mario Galaxy games and Super Mario 3D World.

Super Mario Galaxy series
Blue Lava Bubbles appear as the blue, possibly colder, counterparts to normal Lava Bubbles. They are commonly seen around King Kaliente, who is a boss in Good Egg Galaxy and is one of Bowser Jr.'s commanders. They also appear in Boss Blitz Galaxy (Galaxy 2) and Melty Molten Galaxy (Galaxy). The only way to defeat them is by shooting Star Bits.

Super Mario 3D World
In the Wii U game, Super Mario 3D World, Blue Lava Bubbles are more common than they were in the Galaxy series. There are now stages dedicated to blue lava and the Blue Lava Bubbles, one example being Castle-4: Boiling Blue Bully Belt. Blue Lava Bubbles can no longer be defeated and look slightly different from their other appearances.