Plot
In 1945 Las Vegas, World War II veteran Frank Harris returns to his mother and invites her to a ride on his motorcycle. The duo are involved in a traffic collision where Frank's mother is killed. Afterwards, Frank is inadvertently transported to a cartoon-based alternate universe called "Cool World", where he becomes a detective for its local police department.
Forty-seven years after, underground cartoonist Jack Deebs is released from a ten-year prison sentence for murdering his wife's lover. During his imprisonment, he created a series of comics called Cool World based on recurring visions of his, prominently featuring the sultry femme fatale Holli Would. Holli's wish is to escape Cool World and become a real human being, which is possible when "doodles" (slang for Cool World's inhabitants) have sexual intercourse with "noids" (slang for humans). However, Frank and his doodle partner Nails keep a vigilant eye on Holli to ensure that the two dimensions do not intertwine.
Shortly after his release, Jack is also transported into Cool World and smuggled into a local nightclub by Holli and her henchmen, the Goons. Frank aggressively confronts Jack, explaining that Cool World had existed long before he created his series. He also warns him that writing implements, such as his fountain pen, are lethal to the doodles and to abstain from having sex with Holli, as her transforming into a noid can be risky for both dimensions. Despite these warnings, however, Frank himself is in love with another doodle, Lonette, but limits himself to platonic advances towards her.
Eventually however, Jack succumbs to Holli's advances and she proceeds to seduce and make love to him, transforming her into a noid. She then steals Jack's pen to entrap Nails and leaves with Jack for the real world.
In the real world, Holli is excited and overwhelmed experiencing real sensations. Due to her presence there, she and Jack spontaneously flicker in between noid and doodle forms. While contemplating their situation, Holli tells Jack about the "Spike of Power", an artifact which was the cause of Frank being transported into Cool World and placed on top of the Union Plaza Hotel by a doodle who crossed into the real world, and admits she wants to use it to remain in her noid form permanently. When Jack displays skepticism about the idea, Holli abandons him to search for the Spike on her own.
Frank learns what has happened and returns to the real world, where he reluctantly teams up with Jack to stop Holli. They arrive at the hotel as Holli begins to climb to the top of the tower. In Frank's pursuit, Holli pushed him off the building to his death. As she seizes the Spike, she releases a multitude of monstrous doodles into the real world, affecting its surroundings and transforming Jack into a superhero-based doodle.
Although enticed to begin a new life in the real world with Holli, Jack returns the Spike to its rightful place, sending him, Holli and the invading doodles back from whence the creatures came and restoring the balance between their dimensions. The now-freed Nails brings Frank's body back to Cool World, where he and Lonette mourn his loss.
However, as she learns from Nails that Holli was briefly in her doodle form when she murdered Frank, she explains that a noid murdered by a doodle in the real world can be reborn as a doodle in Cool World. Frank is revived as such, allowing him to continue his relationship with Lonette in earnest. Meanwhile, Jack begins to plan his future with Holli, to her dismay.
