The Dirty Bubble is the 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 his debut 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, he accidentally defeats the Dirty Bubble by popping him with a pencil, which he was using to ask the Dirty Bubble to sign his autograph with. Despite this, he would make return appearances in later episodes.
- 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.
- At one point, he went to Cancun with the Killer Shrimp, as stated in "Mermaid Man and Barnacle Boy V".
- 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".
- Being a bubble, his sole weakness is pointed objects like pencils.
- It has even became a running gag that in just about every episode he appears in so far, he gets defeated by getting poked by something pointy.