While Emma Frost lay in a comatose state, Dr. John Sublime harvested eggs from her to begin experimentation. The Weapon Plus program then used the eggs to create thousands of identical mutant girls in the hope of developing a powerful weapon capable of killing every mutant on Earth by combining their telepathic abilities. The project was designated Weapon XIV, and the girls were incubated and artificially aged inside the subterranean level of The World. While most girls remained dormant, five were sent to infiltrate the Xavier Institute as student sisters to hone their talents for Sublime's purpose.
After the Xavier Institute went public, Phoebe and her sisters were enrolled as orphan quintuplet sisters. To protect their secret origins, the girls unconsciously place mental blocks in the minds of the faculty preventing them from investigating their background.
The girls quickly gained the moniker "The Stepford Cuckoos", though their chosen codename was the Five-In-One. Emma Frost took a special interest in the girls, and the Cuckoos became her protégés.
When Kid Omega led a rebellion of students at the X-Mansion, Sophie encouraged Phoebe and the other Cuckoos to take action, and they covertly snuck into Cerebra. Using Kick to amp up her powers, Sophie and her sisters were able to stop Quire. Unfortunately, Sophie died in the process.
With the death of Sophie, the Five-In-One became the Four-In-One. The girls were furious with Emma Frost, whom they blamed for Sophie's death. This mourning and anger was multiplied when Esme attempted to murder Emma, fled the X-Mansion, and joined Xorn's Brotherhood. With the departure and later death of Esme, the Four-In-One now became the Three-In-One.
When the Institute was rebuilt under the leadership of co-headmasters Cyclops and Emma Frost, the students were organized into several training squads with an assigned mentor staff member. Phoebe and her sisters were assigned to the Corsairs Squad under the tutelage of Cyclops with the girls serving equally as co-leaders of the squad.
On M-Day the vast majority of the world's mutant population was depowered. Phoebe and her sisters retained their powers, but they were three of only twenty-seven students to retain their powers. Fearing for the students' safety, Emma Frost ordered that the depowered students and staff leave the Institute. For their safety, the depowered students were brought through the Morlock Tunnels to an awaiting bus. Unfortunately, the bus of depowered students was bombed by anti-mutant zealot Rev. William Stryker, killing all forty-two of the former students on board.
The remaining students were placed by Emma Frost into an all-out brawl, and the ones deemed the best by Emma would become a group of New X-Men in-training. This entire exercise was met with disgust by the Three-In-One, who promptly informed Cyclops of Emma's actions.
When an unstable fraction of the Phoenix Force sparked inside the girls, their dormant Weapon Plus nanotech inside their bones was activated. This nanotech briefly reanimated Sophie and Esme, who directed their sisters back to The World to activate Sublime's plan for the destruction of the mutant race.
The Phoenix and Sublime both wrestled for control of the Cuckoos when the X-Men arrived. While Mindee appeared consigned to her fate as part of Sublime's weapon, Phoebe fought to embrace the Phoenix. Soon Phoebe was captured and integrated into Sublime's machine, but the Phoenix was able to possess Celeste. When Celeste was finally merged into the machine, the Phoenix was divided between all the Cuckoos and trapped in their newly emerged secondary mutation, organic diamond hearts. This event finally activated the Thousand-In-One.
Celeste continued to resist the Phoenix and Sublime's machine long enough for the X-Men to forcibly disconnect them. In a rage, Phoebe triggered a power surge causing an explosion. However, Celeste was able take full control of the Phoenix, destroyed her sisters, and trapped the Phoenix fragments inside the Three-In-One's flawless diamond hearts rendering them emotionless.
The Quest for Magik
After returning to the Institute, the girls adopted a rebellious/mischievous streak. They helped Elixir telepathically gain a Ph.D. level knowledge of science and biology from Beast's brain. Along with the other students, they were pulled into Limbo, where they were rescued by Prodigy. To repay his kindness, the Cuckoos restored all of the knowledge he had previously gain with the use of his powers despite his powers being deactivated. Phoebe and her sister were briefly considered as potential candidate recruits for the Initiative.
The Stepford Cuckoos rejoined the X-Men and the last of mutantkind in San Francisco. During the Skrull Invasion, they assisted in the evacuation of a San Francisco Hospital, and later offered remote support to Emma while bringing down the Skrulls' psychic blockade.
Once they relocated to Utopia, the Stepford Cuckoos frequently manned Cerebra. When Lobe, with Scalphunter, brought a group of Predator Xs to attack Utopia, the X-Men were forced to battle the mutant eating creatures. The Cuckoos served as telepathic communication for the team, but during the battle the Phoenix fragments that were contained inside their diamond hearts escaped, mysteriously returned to space, and left the girls unconscious. With the loss of the Phoenix, the girls fell into a depressive funk.
When Zero began laying the foundations of mental control for his rebellion against Hope Summers, Phoebe was one of the few mutants unaffected. Due to this mental manipulation, Phoebe was put at odds with her sisters by defending Hope.
After Cyclops and Wolverine decided to part ways, Phoebe wanted to return to Westchester while Mindee wanted to remain on Utopia. With the deciding vote left to Celeste, she opted to stay on Utopia, partly because of Quentin Quire's presence at the school.
When the Phoenix Force returned to Earth searching for a new host leading to the war between the Avengers and the X-Men, the Stepford Cuckoos were among the younger X-Men detained in the Avengers Compound with the Avengers Academy. Afterword they were reluctantly recruited to the new Jean Grey School where the manned Cerebra and witnessed the death of Professor X and the reemergence of mutantkind.
The girls were very displeased with the new school. When Cyclops and his X-Men came to the school looking for recruits to their mutant rebellion, the Stepford sisters and Angel volunteered to go.
Irma had cut her hair and dyed it black to be an individual, and after an encounter with the younger Jean Grey, Phoebe remarked that she would make a good redhead. She subsequently dyed her hair red, just before Magik transported the sisters to Tabula Rasa for training.
Phoebe was one of the many mutant that opposed the crazed X-Man from remaking the world in his image. When X-Man realized he couldn't remake the world as long as the X-Men were around, he made all his enemies vanish in an instant, including Phoebe.
The mutants were sent by X-Man to a different plane of existence he created where he attempted to create a utopia where they and all other mutants would be at peace, altering their memories so they wouldn't resist. Phoebe Cuckoo was employed by Mastermind Studios as a professional assistant to its head, Regan Wyngarde. While not seen, Phoebe was presumably allowed to return to the real world when X-Man decided to release the mutants he trapped in his reality.
House of X
Phoebe and her sisters joined the mutant-only nation of Krakoa. One of their duties was escorting a group of human ambassadors in the Jerusalem Habitat through a Krakoan Gateway so they could meet with Magneto and Emma Frost to discuss potential recognition of Krakoa as an official nation.
Phoebe was secretly dating Quentin Quire, and was hiding the relationship from her sisters, out of a desire to have the relationship all to herself and to not share. Later, she opened her relationship to the public. First with Wolverine and Forge, and eventually her sisters learned about it, mentioning it in the Hellfire Gala. 
She had the habit of restoring Quentin's memories each time he died.
Powers and Abilities
Phoebe's powers are identical to that of her sisters.
Those of her her sisters.
- Phoebe has demonstrated some aggressive behavior especially when the Phoenix came to possess the Stepford sisters. Phoebe desired to embrace the Phoenix and all its destructive power.
- Phoebe has occasionally acted as a de facto leader of the Stepford Cuckoos since the death of Sophie, though more often this role is taken by Celeste.
- Phoebe is the third of the Cuckoos to change her hair.
- 232 appearance(s) of Phoebe Cuckoo (Earth-616)
- 7 minor appearance(s) of Phoebe Cuckoo (Earth-616)
- 9 mention(s) of Phoebe Cuckoo (Earth-616)
- 132 image(s) of Phoebe Cuckoo (Earth-616)
- 3 quotation(s) by or about Phoebe Cuckoo (Earth-616)