Krillin is introduced in Dragon Ball as a rival (and later best friend) of the main character, Son Goku. Later in the series, he can also be seen to have a close relationship with Goku's child, Son Gohan. Krillin eventually settles down and marries Android #18 after the cliff-hanger Cell Games to have a child named Maron.
At the beginning of Dragon Ball Z, Krillin is of the few Z Fighters to survive the fight against Vegeta and Nappa. During the battle he manages to kills three out of six Saibamen, and he travels with Gohan and Bulma to Planet Namek to use the Namekian Dragon Balls to revive their dead friends, since the Earth's Dragon Balls vanished due to Piccolo's death. Once there, they save a young Namekian called Dende from death at the hands of Dodoria, one of Frieza's elite henchmen. After Dende learns of their cause, he leads Krillin to Guru who unlocks Krillin's hidden potential as well as giving the Earthlings their first Namekian Dragon Ball. After a few close encounters with Vegeta, Krillin and Gohan are forced to team up with him in order to fight the powerful Ginyu Force, and although they defeat Guldo with Vegeta's help, they are still defeated by Recoome. Luckily, Goku arrives and defeats the Force with ease. Krillin is shortly after involved in a battle with Captain Ginyu, who has taken over Goku's body, and together with Gohan deals him enough damage that Ginyu is forced to find a new strategy. A prominent episode that was heavily edited for North American broadcast featured Frieza, in his second form, impaling Krillin through the chest and disposing of his body in a lake, leading to Gohan furiously attacking Frieza and nearly being killed. However, Dende was able to heal Krillin, who launched a surprise attack and severed Frieza's tail before Gohan was killed. Later in the saga, they thought Frieza to be defeated by Goku's enormous Spirit Bomb, Frieza reappeared and used his abilities to lift Krillin high into the air and detonate him from the inside, killing him instantly. His death enrages Goku, causing him to become a Super Saiyan, and from there, defeat Frieza. Krillin is later revived by the Namekian Dragon Balls.
During the Garlic Jr. Saga (anime only), Krillin plays a lead role along with Gohan and Piccolo. He introduces his first girlfriend, 'Maron'. When everyone is affected by the Aquamist, only Krillin, Gohan, Piccolo, Maron, Kami, Mr. Popo, Yajirobe, Korin and Haiya Dragon are unaffected. Gohan and Krillin lead an assault on Garlic Jr. and the Spice Boys for the Ultra Holy Water, the only cure. Krillin faces Tarudo and protects Gohan from an attack by Zald, causing Gohan's anger level to rise, resulting in the deaths of Zald and Tarudo. Piccolo, now seemingly affected by the Aquamist, bites Krillin and both begin to attack Gohan. However, this was a staged diversion to free Kami and Mr Popo. Krillin and Gohan fight Gayishu and Vinaiga and they are quickly dispatched. Together with Piccolo, they then fight Garlic Jr. long enough for Kami to release the ultra holy water. His plans foiled, Garlic Jr. re-opens the Dead Zone only to be sucked in again. After the fight and a failed effort to propose, Krillin decides to break up with Maron, considering himself to be not good enough for her.
During the Android Saga, Krillin trains for the three years and is on the front lines in all the fighting, tagging Dr. Gero to his base and reporting it to the Z Fighters. When the Androids, #16, #17 and #18 are released he stays out of the fight due to fear. He becomes infatuated with the female #18 which causes him to resist deactivating her with a controller Bulma created, though because of this, regardless of his efforts, Cell is able to absorb her and achieve his perfect form. Krillin is the first to face Cell in his perfect form and is defeated with one kick. He later participates in the Cell Games, a martial arts tournament created by Cell for entertainment, and fights one of the Cell Juniors who attack the Z Fighters, though he is easily beaten. He is saved from the Cell Juniors by Gohan who achieves Super Saiyan 2. During the final beam struggle in the anime between Gohan and Cell, Krillin, Tien, Yamcha, Piccolo and Vegeta try to help him (in the manga only Vegeta helps). Krillin uses the second wish to remove the bomb from #17 and #18.
By the time of the Great Saiyaman Saga, Krillin has quit fighting, married #18, and has a daughter named Marron. However, after learning of Goku's return from the Afterlife to compete in the 25th World Tournament, he decides to also participate (after 18 orders him in hopes of winning the prize money). After the Supreme Kai enlists the Z Fighters to help him defeat the wizard Babidi, Krillin joins them, but is turned into stone by Dabura, along with Piccolo. He is later released after Dabura is killed by Majin Buu. Krillin is later turned into chocolate and eaten by Super Buu, losing his life for the third time. Only in anime filler, while in Other World, Krillin, Yamcha, Pikkon, Olibu fight Kid Buu to no avail and are almost destroyed. During Goku and Vegeta's fight against Kid Buu, Krillin is brought back to life by the Namekian Dragon Balls and gives his energy to Goku's Super Spirit Bomb, which is used to destroy Kid Buu and return the world to peace.
His role in GT is minimal with a brief cameo in the Baby Saga. In the Super 17 Saga, he is killed by Android #17. He is revived by Shenron after the defeat of Omega Shenron and has a match with Goku, which he wins.
Krillin is seen in 2 of the Dragon Ball films, 12 of the Dragon Ball Z films, is seen briefly in the History of Trunks TV special and is shown in the Bardock - The Father of Goku TV special through future glimpses of Goku and Krillin's training with Roshi.
Dragon Ball
Dragon Ball Z
As well as all of the Supersonic Warriors, Shin Budokai, Budokai and Tenkaichi video game series. He is also in the game Burst Limit as both a playable character and support character.
This only includes games from the Game Boy Color, Game Boy Advance, Nintendo DS, Nintendo Gamecube, Nintendo Wii, Playstation, Playstation 2, Playstation 3, Playstation Portable, Xbox and Xbox 360.