- “And you are?"
"Negasonic Teenage Warhead."
"Negasonic Teenage... What the shit?! That's the coolest name ever!”
- ―Deadpool and Negasonic Teenage Warhead meet for the first timesrc
Negasonic Teenage Warhead (born Ellie Phimister)  is a mutant and a member of the X-Men, formerly under the tutelage of Colossus. She possess the mutant ability to detonate atomic bursts from her body.
- “And you chicken noodle, "nothing compares to you". Sinéad O'Connor, 1990. Sorry."
"It's all right. You're cool.”
- ―Deadpool and Negasonic Teenage Warheadsrc
After spotting Deadpool on the news, Colossus took Negasonic Teenage Warhead with him in an attempt to convince the mercenary into joining the X-Men. However, Deadpool declined and ended up fleeing from the mutants. Later, the mercenary would enlist the two mutants' help in saving Vanessa Carlysle and defeating Ajax. During the ensuing fight, Negasonic Teenage Warhead used her powers to take out multiple soldiers and save Colossus from getting strangled by Angel Dust. At the battle's conclusion, Negasonic Teenage Warhead, after acknowledging a reference from Deadpool, left the area with Colossus as the mercenary reunited with Vanessa
Negasonic Teenage Warhead was at the X-Mansion with fellow X-Man and girlfriend Yukio when Colossus bought Deadpool there to recover after the latter blew himself up. When Colossus convinced Deadpool to join the X-Men, she joined them on a mission to stop a trouble mutant causing trouble at the Essex House for Mutant Rehabilitation. During the mission, Deadpool managed to talk the young mutant, Russell Collins, down but then proceeded to kill some of the orphanage's staff when he learned that they were abusing Russell. Deadpool was subsequently arrested.
Colossus, Negasonic and Yukio later travelled to the Essex House to back up Deadpool, Cable, and Domino in taking on Juggernaut. Negasonic and Yukio helped to evacuate the children from the orphanage, then assisted Colossus in taking down Juggernaut.
Sometime after, Negasonic and Yukio repaired Cable's time travel device and gave it to Deadpool, allowing him to travel though time to save Vanessa Carlysle and Peter, and to kill an earlier incarnation of himself and Ryan Reynolds before he made Green Lantern.
The Westchester Incident
In 2028, Charles Xavier developed Alzheimer's and suffered a massive seizure that injured 600 people, and killed 7 mutants, including several members of the X-Men. It is unknown if Negasonic Teenage Warhead was among those who were either killed or injured.
Negasonic is portrayed as a calm, snarky, sarcastic, unmotivated, antisocial, yet good humored and patient teenager, even her outrageous mutant name is a good indicator of how little she cares about what anybody thinks of her. Whilst Deadpool seems to expect her to be a stereotypically angst teenager, which she does not deny, she is shown to possess a genuine heroic personality.
Negasonic can also be somewhat rude, as she isn't afraid to insult people whom she doesn't like, especially Deadpool, such as calling him "Douchepool" when she tried to tell him that Ajax got away, and "old" due to him referencing Alien 3. She would even take a moment to write a Twitter post on her phone right at the start of a battle. Despite being somewhat moody at first, Negasonic is entertained by Deadpool's feeble attempts to hurt Colossus, giggling as he fails to do so. She does eventually warm up to Deadpool, calling him "cool" after they defeated Ajax and successfully saved Vanessa Carlysle. Negasonic can also be very decisive in combat, not hesitating to attack Angel Dust, providing Deadpool with the means to reach Ajax, and saving Colossus in time.
Negasonic appears to possess a close relationship with her mentor, Colossus. Whilst she seems to dislike his gentle, hard-working, and serious nature, Negasonic does not undermine or argue against him. A further testament of their close relationship, is that Negasonic almost risks herself to save Colossus as she renders herself unconscious using all her power to save him, despite the risk of collateral damage killing her.
Powers, Abilities & Weaknesses
- “Oh I so pity the dude that pressures her into prom sex.”
- ―Deadpool, after seeing Negasonic's powers being used to blast away Angel Dust.src
- Self-Detonation/Explosion Manipluation - Negasonic Teenage Warhead possesses the ability to generate explosions from her body of varying degrees. At lower levels, she can send a car flying away, crushing two enemies. At higher power levels, she was able to level an entire scrapyard and destroy a grounded helicarrier. Negasonic can infuse the explosions she creates with her physical combat. She can use her powers in conjunction with a full body charge to attack superhumanly strong opponents such as Angel Dust. She can also use her explosive powers to cause a downward explosion capable of launching herself high into the air.
- Skilled Engineer - Negasonic was able to fix Cable’s futuristic time travel device, however she instantly regretted it after Deadpool took it.
- Concentration/Charge Time - Negasonic does seem to require a certain amount of concentration and charging time in order to better control the size, shape, and direction of her explosions. Momentum also appears to play some part in the overall force and general direction of her explosions.
- Physical Exhaustion - While Negasonic Teenage Warhead can create explosions at different levels, she becomes fatigued at higher levels. After she charged at Angel Dust with this power, Negasonic was temporarily dazed from the explosion she created. When she used her power against Angel Dust a second time, leveling the scrapyard and toppling a helicarrier as a result, Negasonic was rendered unconscious for a short time.
- Vanessa Carlysle - Rescuee and Ally
- Firefist - Ally
- Unlike other characters in the Marvel Comics Negasonic Teenage Warhead is a character not born in a real location. She was from Genosha.
- Due to the popularity of her character in the movie, Negasonic Teenage Warhead has been revived in the comics. Her appearance now matches her film counterpart.
- During San Diego Comic-Con 2015, Brianna described her character as a "15 year old superhero in training".
- Ellie can be seen wearing an 'X-Men' uniform similar to the one from X-Men: First Class.
- Brianna Hildebrand created a rock playlist for Ellie, which for obvious reasons included the song which inspired her codename (along with others by its band, Monster Magnet). 
- ↑ Official Deadpool Twitter account
- ↑ Brianna Hildebrand Official Twitter account
- ↑ ‘Deadpool': Brianna Hildebrand on Negasonic Teenage Warhead, Ryan Reynolds, and More