In the original TMNT animated series, April O'Neil (whose middle name was purported to be Harriet) was a television reporter for Channel 6 News. She was employed by Burne Thompson, though due to her headstrong nature and passion for her work, she expressed frequent disagreement with the assignments he gave her. She also butted heads on a regular basis with Vernon Fenwick, the director/camera operator whose enormous ego compelled him to scoop April on her stories whenever possible. April was best friends with Irma, the secretary at Channel 6. Though it remains unclear whether this was required work attire or her particular fashion sense, April could usually be found wearing a distinctive yellow jumpsuit. She lived in an apartment in New York City, though during the course of the series, she was forced to relocate several times due to a variety of indirectly Turtle-related mishaps.

In 1987, having been employed at Channel 6 for less than a year, April was reporting on a series of thefts of high-tech scientific equipment, apparently by a ninja (ostensibly components Shredder was securing for use in the Technodrome), when she came under attack by a gang of punks. Thinking quickly, she managed to squeeze into a storm drain and ran from the mob until she hit a dead end. As it happens, the Ninja Turtles were nearby and soundly beat the punks. They took her back to their sewer lair for rest and recovery where they explained their origins to her. At first, she believed them to be responsible for the equipment thefts, but they agreed to provide her with the true culprits if she provided her assistance. April quickly became the Turtles' link to the outside world, since their unusual appearance effectively precluded them from functioning aboveground without some sort of disguise.

April's friendship with the Turtles resulted in the opportunity to film exclusive footage of their encounters with Shredder, but despite her intimate knowledge of the details of their lives, she tended to keep her professional news reports about them impersonal and mysterious. She was a vocal champion of their cause, despite the opinion of the general populace (an opinion shared by Burne Thompson) that the Turtles were a menace to the city. Through no fault of her own, April was frequently captured by Shredder, quite often as bait in order to lure the Turtles out of hiding in order to unleash his latest attempt at destruction upon them. April's innate curiosity and determination placed her in danger on several occasions as well. The Turtles usually waited until the last possible second to rescue her, but they always came through in the end. Her most important contribution to the Turtles was her experience in doing research on the Channel 6 computers and alerting the Turtles to trouble and possible case leads.

Like Lois Lane before her, April was normally portrayed as a capable woman, but also filled the role of the typical plot device of damsel-in-distress. Her obsession with "getting a story" led to numerous instances of poor judgement which often resulted in her getting captured for the Turtles to save.