From Sonic Retro
Bubbles, or Harisenbo (ハリセンボ) in Japan, is a puffer-like badnik from Sonic the Hedgehog 3 found in Marble Garden. It is similar in both behavior and appearance to the Pointdexters found in Hydrocity Zone. They are primarily blue in color. Bubbles are known for their spikes, which they can retract and protract at ease. Bubbles can also float in the air, meaning they can be a difficult badnik to predict. They can only be defeated if they are hit without their spikes showing. Attempting to hit a Bubbles badnik while they have their spikes protruding will result in the loss of a shield, rings, or a life.
Bubbles returns in Sonic the Hedgehog 4 Episode I, mostly used for a Homing Attack chain. Whilst they don't move around and only float, they act slightly differently depending on their colour. Blue versions have no spikes while red Bubbles have retractable spikes, making chains harder.