April O'Neil is a teenage girl with black eyes, thick eyelashes and curly burgundy hair with bangs and worn in two high buns. She often wears a pair of red cat-eye glasses with yellow lenses.
April wears a black choker around her neck, a long yellow t-shirt and a green varsity jacket with quarter sleeves, pale green trim and stripes, single button, and an "5" logo over the jacket's heart and back. She also wears black leggings and yellow sneakers.
In "The Purple Game", her pajamas consists of a blue tank top with yellow short sleeves and a pink cat print on the center, a pair of green pajama trousers, blue-and-dark blue pattern socks, and green silk nightcap.
In the 3rd part of the shows finale, she wears a green and white dress, a cropped yellow hoodie, and long black fingerless gloves. She also has her hair in a ponytail rather than pigtails.
April is very upbeat, sassy, and much louder than her previous incarnations. She is also aggressive and quick to jump into action, showing that she also has more spunk, confidence, and spirit.
April is shown to be incredibly brave as seen in "The Gumbus" when she was enjoying the whole fiasco in the Stock 'n' Shop while Mikey and Leo were freaking out. In "War and Pizza", April is very determined and would never give up as seen when she tries to get through Timmy's birthday without any disruptions.
Despite this, she can be rude at times. Like in "The Fast and the Furriest" when Donnie accuses her of stealing the Turtle Tank and, being annoyed by them breaking in and being accused of something she didn't do, uses a bat to get them out via the window.
April is always helpful as seen when she uses her birthday wish to help Warren Stone save Hypno-Potamus. Even though she was betrayed by Warren, she is quite forgiving when she decides to save him from Baron Draxum with the help of Hypno-Potamus. April is also selfless as she decides to cut off Warren's arm which contains the gauntlet for the sake of Hypno-Potamus.
In "Always Be Brownies", April has some insecurities as seen when she was trying to sell cookies but can't due to her passive-aggressive approach.
April is a true New Yorker and a real firecracker: upbeat, wisecracking, and confident. As the Turtles' only ally, she loves them like brothers—and along with her pet, Mayhem joins them on all their epic adventures.
She's quite agile and powerful on her own. Her fighting style screams out Street Fighting. She also has a natural talent for improvisation. April has also showcased several ninja skills, such as blending in with her surroundings, acrobatics, and showing some signs of being knowledgeable about ninjutsu.
- Baseball bat: Her main weapon. It was a normal bat until the events of "Donnie vs. Witch Town", wherein it was infused with the magic inside Gentry's miniature cauldron, thus becoming a mystic weapon.
- Giant spatula: Used in an online motion comic to attack Meat Sweats.
- Smack-a-Vole mallet: Used in "War and Pizza" to attack animatronic voles animated by Albearto.
- Green staff: Used in "Mystic Mayhem" to attack Huginn and Muninn.
- Makeshift "bow and arrows": Used in "The Gumbus" to attack the robotic Gumbus; they are made out of a rolling pin and sausages, respectively.
- Ring blade: "Borrowed" from Hypno-Potamus in "Warren & Hypno, Sitting in a Tree", and used to cut off Warren Stone's arm which contained a gauntlet.
- Mop: Used in "Always Be Brownies" when she was fighting the Brownie Clan.
- Tray: Used in "Always Be Brownies" during her battle against Julia.
- It revealed in "Cloak and Swaggart" that April has skill in cooking.
- April's parents
- Hamato Clan: She has been a friend of the family for years, but she had become family to the clan long ago. This has allowed April to tap her own Hamato Ninpō power.
- Hamato Karai: In "Anatawa Hitorijanai", Karai reassured April that she had always been part of the family. After Karai died, her spirit redided inside April so that Karai, through April, could help the brothers master the Hamato Ninpō in order to defeat the Shredder.
- Hamato Yoshi / Lou Jitsu / Splinter: They share great chemistry and trust for one another, both as friends and as fellow ninja. April usually addresses Splinter as "Splints." More than once, when Splinter accompanied April to the surface, he disguised himself as a human teenager named Randall.
- Mad Dogs: They are April's closest friends, and she is like a big sister to them. She often fights alongside them.
- Donatello: April and Donnie are close friends, though they do seem to argue usually, if only to a slightly moderate degree.
- Leonardo: Leo is April's second best friend. They are close in some adventures. Leo and Mikey both like to play with her.
- Michelangelo: April is like an older sister to him. Mikey loves hanging out with April whenever he has the chance. April and Mikey together are the ones most responsible for helping Baron Draxum adapt to his new life.
- Raphael: They have a good relationship. Raph, as the leader, takes care of her.
- Mayhem: Mayhem becomes her pet and closest companion so far. When April is in trouble Mayhem tries his best to find a way to protect her.
Friends and allies
- Todd Capybara: April and Todd worked together as part of the B-Team in "End Game". Todd later served lemonade to April in "Battle Nexus: New York". His Cuddle Cakes Puppy Rescue was a safe haven for April and the Mad Dogs after the destruction of the lair and during April and Karai's teaching of the Hamato Ninpō to the Mad Dogs.
- Baron Draxum: They started off as enemies throughout season 1. As seen in the season 2 episode "Repairin' the Baron", Draxum moved into the apartment directly above April's in the same building. Once Draxum became a more regular part of the family life, he started working at Autry Cafeteria in April's high school. In "Mystery Meat", April is shown to help monitor Draxum's situation, including helping him adapt to his new human workplace, conceal both his Yōkai identity and mystic power, and reel in some of his old bad habits. Over time, April and Draxum were shown to have become unlikely friends and allies with a good working relationship. As friends, April usually addresses Draxum as "Barry," while Draxum usually addresses April simply as "O'Neil."
- Franken-Foot: April and Franken-Foot worked together as part of the B-Team in "End Game".
- Gentry: April and Donnie befriended Gentry during their visit to Witch Town in "Donnie vs. Witch Town". The mystic power of Gentry's pot accidentally transferred to April's baseball bat, finally giving April a mystic weapon on par with those possessed by the Mad Dogs.
- Cassandra Jones / Foot Recruit: April and Casey were enemies for most of the series, but Splinter, who had befriended Casey in "Always Be Brownies", tried unsuccessfully to get April and Casey to set aside their differences. April and Casey wouldn't join on the same side until they helped the Hamato Clan destroy the Shredder in "Rise".
- S.H.E.L.L.D.O.N.: April and S.H.E.L.L.D.O.N. worked together as part of the B-Team in "End Game".
- Stanley / Bullhop: April and Bullhop worked together as part of the B-Team in "End Game".
- Sunita: She is April's friend and lab partner in biology class. Like April, Sunita also wants some "normalcy" in her life, despite being a Yōkai concealed in the human world. They hang out very often.
- Albearto: April fought Albearto when he came to life and terrorized several children at Timmy’s birthday party.
- Big Mama: April, Draxum, Foot Recruit, Splinter, Todd and New York City's entire population were trapped inside the Mystic Orb in "Battle Nexus: New York". After Draxum helped April, Foot Recruit and Splinter to escape, April helped the group oppose Big Mama.
- Foot Clan: April was unwittingly working for them as an employee of the Foot Shack. However, upon learning the true nature of her employers, she aided Splinter in his attempt to keep a piece of the Kuroi Yōroi out of the Foot’s possession.
- Kendra: April has known Kendra since kindergarten. Their full personal history is unknown, though it is heavily implied that they hate one another.
- Mezmer-Ron / Hypno-Potamus: April confronted Hypno-Potamus during his attempt to make her high school disappear. But later helped him rescue his "best friend/roommate/it’s complicated", Warren Stone.
- Baxter Stockboy: April helped expose Baxter's monster hoax in "The Gumbus".
- Warren Stone: April is a fan of Warren Stone, and has been part of the Warren Stone Fan Club since 2010, even after he deliberately put her and the Mad Dogs in danger in his and Hypno's conflict with Baron Draxum.
- Rupert Swaggart / Meat Sweats: April helped Sunita retrieve the cloaking brooch that Meat Sweats had stolen from her friend Sunita.
- Dale: A fellow student at April's high school. Dale has a crush on April that she does not return. April does not want Dale to be harmed, though.
- Taylor Martin: A popular girl at April's high school who April tried unsuccessfully to befriend.
- "Game on!"
- "Aprillllll O'Neil!" (Her catchphrase, often heard before she charges into battle)
- "Hey, Mayhem. Now that's a cute name!" - "Mystic Mayhem"
- "That's enough! I just need him to sing 'Happy Birthday' and quiet the kids down so I don't get fired." - "War and Pizza"
- "That was fast. Actually, I just needed Donnie." - "War and Pizza"
- "Hi, Donnie! You have nine seconds to tell me why you just broke my door." - "The Fast and the Furriest"
- "Is anybody there?!" - "Mrs. Cuddles"
- "Is my acting that bad?" - "Mrs. Cuddles"
- "Man, wish I could fight with the fam!" - "Shadow of Evil"
- "No. I've seen weird, and that is not it. I'm April." - "Operation: Normal"
- "Best birthday ever~!" - "Warren and Hypno, Sitting in a Tree"
- "You guys crushed it!"
- This version of April marks the second time she is unambiguously portrayed as black in a licensed TMNT work, and the first time a version of her primary character model is portrayed as such. The original version of April O'Neil in the Mirage continuity was inspired by co-creator Kevin Eastman's former wife, the late April Fisher, who was a biracial woman. The fictional April's earliest appearances were in a state of flux, with her first and second appearances in "TMNT vs. the Mousers" and "The Great Chase" appearing caucasian, but her third appearance in "Rescuing Master Splinter" portrayed her more closely resembling the real-life Fisher and with a more ambiguous racial appearance. April's character model would soon stabilize into a black-haired caucasian woman, with the exception of the colorized second printing of the Guest Era story "Egyptian Adventure" where she was portrayed as black. While other incarnations of April would change certain details such as her hair color, they were all portrayed with a caucasian primary character model until the version of her character designed for Rise of the TMNT.
- This is also the first time April is changed from caucasian to African-American.
- This is the third teenage incarnation of April after the TMNT & Other Strangeness version of her and the 2012 incarnation of her. This is also the second teenage version who is attending high school in-story, as the TMNT&OS version is 19 and has already graduated from high school.
- In this incarnation, April has a pet mutant named Mayhem.
- A running gag in this series is April having a different job almost every time she appears, with her period of employment usually ending by, or before, the end of an episode.
- According to one of her official character bios, April is revealed to have a job at a pizza shop, which is how the Turtles get their pizzas in this series.
- The Turtles also get a friends and family discount because of their connection to April.
- It is unclear, however, if this is actually the case in the series itself, she is never shown delivering pizza except in the comics.
- She gets fired from her job at a restaurant called Albearto's after the events of "War and Pizza".
- In "Mrs. Cuddles", April works as an actress on Mrs. Cuddles' television program.
- In "Shadow of Evil", April works at a shoe store called the Foot Shack.
- According to one of her official bios, April loves the Turtles like brothers.
- According to the Junior Novel "Ninja Power", April is 16 years old and she has known the Turtles for 5 years.
- As revealed in "Warren and Hypno, Sitting in a Tree", April has been a member of the Warren Stone Fan Club since 2010.
- As mentioned by Donnie in "Operation: Normal", April seems to have a fear of cosplay wizards.
- As shown in "The Purple Game", April has shown to be skilled in video games.
- Also shown in "The Purple Game", April lives with her mother.
- April apparently has a crane license.
- Even though she isn't one of the Turtles, she tends to act like the second-in-command to Raphael.
"Not only will she be played by a black actress, but reports indicate that she will also apparently be a black character in the cartoon."
"April O’Neil is Black – Although the character has traditionally been depicted as a redhead, Nickelodeon has decided to give her a slightly different background this time around."