The Dirty Bubble is the arch nemesis of Mermaid Man and Barnacle Boy. His form is that of a giant, dirty bubble, hence his name. He can capture an object by landing over it and sucking it in. In the episode "Mermaid Man and Barnacle Boy II", he suddenly appears and attacks Mermaid Man and Barnacle Boy, trapping them inside him. When SpongeBob emerges from the diner, having found the Mermaid Man and Barnacle Boy theme song on the jukebox, he defeats the Dirty Bubble by popping him with a pencil which he claims was for the Dirty Bubble to sign his autograph with (it is uncertain whether he actually wanted his autograph and the popping was inadvertent, or if SpongeBob was simply adding humor/irony to the situation). Dirty Bubble returns (probably from someone dipping a bubble wand in the popped bubble liquid and reblowing him), alongside Man Ray, alive and well, in "Mermaid Man and Barnacle Boy V". In the episode, Man Ray has teamed up with him to form an organization called E.V.I.L. (Every Villain Is Lemons). When Barnacle Boy tires of Mermaid Man treating him like a little kid, he joins the two, and commits crimes. In the end, Barnacle Boy returns to the good side, leaving Man Ray and Dirty Bubble disappointed. He is a champion at paddleball, as seen in Have You Seen This Snail?. His name might be derived from an episode in an old TV show called "The Wild Wild West" with an episode being named "Night of the Deadly Bubble."
- In "Have You Seen This Snail", the "Dirty Bubble Challenge" on the Mermaid Man and Barnacle Boy paddle ball set implies that the Dirty Bubble is able to hit a paddle ball the absurdly impossible number of 29,998,559,671,349 times in a row. It is extremely unlikely that this is true, especially since he has no hands and therefore no articulation or coordination to play paddle ball with. However, Patrick claims to have achieved the number in the challenge.
- In "Mermaid Man and Barnacle Boy II", he was voiced by an All Dogs Go to Heaven star, Charles Nelson Reilly. In "Mermaid Man and Barnacle Boy V", he was voiced by Tom Kenny. In Lights, Camera, Pants!, Charles Nelson Reilly voiced him.
- In 2007, his first voice actor, Charles Nelson Reilly passed away from complications of pneumonia.
- In Mermaid Man and Barnacle Boy V, it is shown that the Dirty Bubble can make a human hand with fingers as demonstrating when he pointed into a boat. This may be how he made the "Dirty Bubble Challenge" (see above).
- Being a bubble, his sole weakness is pointed objects like pencils.