Dr. Harley Street was an astronomer working at the MASA Space Center, and the kat behind the creation of the advanced deep space probe called Kat Sat 1, which he was able to finish despite almost having his funding cut off. Unknown to anyone, the probe returned from its astral journey with an unwanted stowaway: a fertile Ci-Kat-A queen. After promising Ann Gora an interview once he had examined the probe, Dr. Street took the Kat Sat 1 back to his lab at MASA There, he finally noticed the yellow goo clinging to the side of the hull, which contained the alien.
Like any good scientist, Street examined it, careful to put on protective latex gloves first. Not that it made much of a difference. He was bitten on the finger by the queen Ci-Kat-A, her mandibles easily piercing the glove. Thus, Street's mind was brought under her control. He vowed to do everything in his power to help her infest Megakat City, starting with MASA Because the Ci-Kat-A fed on radioactive materials, Dr. Street took the queen to the space center's nuclear reactor, making the guard on duty "one of them" in the process. Within the reactor, the queen laid her eggs.
The following day, Ann Gora arrived at MASA for the promised interview, her camerakat Jonny in tow. Busy with plans for world conquest, Street rudely shrugged her off. This only made the reporter all the more curious about what was going on, and in short order she and Jonny stumbled onto the alien's plans. This brought the Swat Kats and the Enforcers, and had their paws full with the queen Ci-Kat-A's newly hatched drones, who began to bite and infect more of the MASA staff and even some of the Enforcers. The Swat Kats managed to sneak into the space center, and they found Ann and Jonny hiding in a space shuttle. Seeing them on a viewscreen in the control room, Dr. Street realized he had an excellent opportunity to get rid of the Swat Kats.
He launched the shuttle, but the vigilantes escaped before the ship went into orbit by jumping out and using their delta backpacks to carry them and the Kat's Eye News crew to safety. In short order, all the Ci-Kat-A drones were destroyed by the Swat Kats and Commander Feral. Street, already worrying about how to feed his alien masters because the MASA reactor had run dry, decided to kill two birds with one stone and escaped with the queen in a van armed with a chain gun for security purposes. They headed to the Megakat Nuclear Plant, where the queen overpowered the technician on duty and grew to enormous proportions by feeding on the reactor.
By now, Street was slowly beginning to transform into a Ci-Kat-A himself from the bite; he already had insectoid compound eyes, but now his hands and arms began to change, becoming more buglike. Street and the queen then proceeded to find a new nesting place for her brood - the penthouse of Megakat Tower, recently reopened since the last incident involving Dr. Viper. He chose this specifically because he knew the tall building would remind the queen of her low-oxygen home world. Deputy Mayor Briggs came up to the penthouse unaware of the alien's plans to get it ready for Mr. Young, who was still interested in renting the building.
She found thousands of Ci-Kat-A eggs, and an even further-transformed Dr. Street. Sporting mandibles, antennae, and soon wings, Street attempted to turn Callie by biting her. Fortunately, though, she'd managed to contact the Swat Kats before his attack. The Turbokat was soon outside the window, and an Octopus Missile was fired and hit Street right in the face. He was sent flying back right through the window, and presumably plummeted to his doom 300 stories below. As for the rest of the Ci-Kat-A, the queen and all her eggs were successfully destroyed by the Swat Kats and the Enforcers.
- Street was slated to appear alongside Dr. Viper in a second episode entitled Doctors of Doom, before the series was canceled. He and Viper would team up to create an army of monsters that would have to be destroyed within twenty minutes of their creation.
- It is possible that Street's name is a reference to London's famous Harley Street, which is known for its various physicians' offices.