Pink Unicorn Island is one of at least two Hawaiian islands available for short-term rent somewhere near Wa Ta Lot Ta Hoie. It directly overshadows Skull Island. Despite its comical appearance, Pink Unicorn Island is considerably larger and cheaper than its neighbouring island. Those who rent it also get a Pink Unicorn Island bathrobe for free. After it turned out that Skull Island was booked, Heinz Doofenshmirtz somewhat reluctantly settled for making his evil hideout in Pink Unicorn Island. His reason for this was because the island was a dormant volcano that held a primordial ooze that could affect the evolution of presumably all living things. This ooze was a key ingredient in the De-Evolution-inator, which was designed to devolve the residents of the Tri-State Area into their genetic ancestors, the Pliopithecus species. This would have allowed Doofenshmirtz to easily take over. After the evil scheme was foiled, Pink Unicorn Island was abandoned by the now-devolved Doofenshmirtz.
Pink Unicorn Island is shown to be home to a small number of cats, who were briefly convinced that the De-Evolution-inator was a real fish.