On each turn, Dubblie creates a new Bubble, pushing it out in the direction he is facing.
If the line he appears in is already filled with Bubbles from Dubblie all the way to the wall he is facing, he cannot push out a new one. Also, Dubblie cannot push the Ghost, so on Ghost Levels, if the Ghost appears in the same row as Dubblie, the Ghost can block Dubblie from generating new Bubbles.
Dubblie can be destroyed in the same way as normal Bubbles, such as by a direct hit from the Shooter Bubble.
When Dubblie is frozen within Ice, he does not generate new Bubbles.