Cell is the villain of one great arc, the one that bears his name in Dragon Ball Z, but his shadow stretches much further: he turns up in Hell in the Z anime, again in GT next to Frieza and, decades later, in a version built by the Red Ribbon Army on the big screen. The whole character is covered in Cell's profile; here we trace what he does arc by arc, from an empty shell found in the woods to Gohan's Kamehameha.
Dragon Ball Z
Cell Saga (episodes 140-194)
The Cell Saga opens with a mystery: a second time machine, identical to Trunks' own, and next to it the discarded shell of a strange creature. Soon after, the people of an entire town vanish, and in episode 142 the culprit shows himself to Piccolo: Cell, a creature with Goku's and Frieza's energy who can even fire a Kamehameha. In episode 143 he reveals his origin: an artificial being created by Dr. Gero's computer from the cells of Goku, Frieza and other great fighters, who has come from the future to absorb Androids 17 and 18. In his own timeline the androids had already been destroyed, so he killed Trunks, took his time machine and travelled four years back. Meanwhile Trunks and Krillin find this era's Cell still incubating in Gero's lab, and destroy it.
Cell feeds on the people of one town after another until he catches Piccolo fighting Android 17. He knocks the Namekian out, withstands Android 16's assault and in episode 152 absorbs 17, becoming Semi-Perfect; he even tries to fool Android 18 by mimicking her brother's voice. Tien holds him down with his blasts until Goku arrives to whisk him away. Then Vegeta emerges from the Hyperbolic Time Chamber and outclasses him. Cell plays on the Saiyan's pride, claiming he would be a better opponent in his perfect form, and Vegeta lets him: Cell blinds everyone with the Solar Flare and absorbs 18. In episode 160 he reaches his perfect form and floors Krillin with a single kick. Vegeta and Trunks can't stop him, and Cell announces a tournament: the Cell Games.
After ten days of waiting the contest begins. Cell swats Mr. Satan aside, then takes on Goku in a long duel until Goku, to everyone's surprise, gives up and sends in Gohan. Cell wants to see the boy's hidden power in full: he spawns seven Cell Juniors and crushes Android 16's head, and the rage turns Gohan into a Super Saiyan 2. Battered, Cell spits out Android 18, reverts to his Semi-Perfect form and tries to blow himself up along with the Earth, but Goku teleports with him to King Kai's planet and dies in the blast. Cell regenerates from his core, stronger than before, kills Trunks and challenges Gohan to a Kamehameha clash: in episode 191 Gohan, urged on by his father's voice and helped by Vegeta, releases all his power and wipes him out. In Trunks' future, meanwhile, that timeline's Cell tries the same plan years later, but a much stronger Trunks destroys him with ease.
Other World Tournament Saga (episode 195)
In the anime Cell ends up in Hell, where he runs riot with Frieza. In the Other World Tournament Saga Goku and Pikkon are sent to calm things down, and in episode 195 Pikkon deals with Cell and the others in no time.
Dragon Ball GT
Super 17 Saga (episodes 42-44)
In GT Cell reappears in Hell alongside Frieza, when Dr. Gero and Dr. Myuu trap Goku down there. In the Super 17 Saga the two face a Goku who is a child again and come out humiliated; in episode 43 they imprison him with a combined technique and leave him frozen in the depths. Goku breaks free, freezes the two villains in turn and accidentally smashes them to pieces.
Movies
The original Cell doesn't return in Dragon Ball Super, but in Dragon Ball Super: Super Hero (2022) the new Red Ribbon Army uses his blueprints to build Cell Max, a red-armoured variant modelled on the Semi-Perfect form. He can't regenerate, and Magenta activates him before his mind is complete, so he becomes a monster that destroys everything in sight.
Did you know? Toriyama didn't originally plan for Cell to transform: he gave him the ability after his editor Yū Kondō called the character ugly, and it was Kondō again who pushed for the second form to make way quickly for the next one.
Our take
Followed arc by arc, Cell has an unusual trajectory: he appears in essentially one storyline, but that storyline builds him with a thriller's patience. First he is an empty shell, then a voice explaining where he came from, then a predator who grows with every absorption. He is the first villain born from the heroes themselves, with their cells and their techniques, and in a sense he is the offspring of Goku's own battles.
The Cell Games are also where the series hands the baton from Goku to Gohan, and Cell plays his part with an almost theatrical vanity. His later appearances in Hell are fun but marginal: the character lives entirely in that one arc, which is exactly why he remains so recognisable.
For his fellow inmate in Hell see Frieza saga by saga, for the android Cell absorbs Android 17 saga by saga, and for the boy who beat him Gohan's profile.