WARNING: The following article contains spoilers for Dragon Ball Super Chapter 76, by Akira Toriyama, Toyotarou, Caleb Cook and Brandon Bovia, available now in English through Viz Media.
The latest chapter of Dragon Ball Super has reignited interest in Goku's long-deceased father, Bardock. He was even trending on Twitter after the revelation of a connection between himself and Granolah, where the latter learns that Bardock once saved his life. It's been quite a while since Goku's father was the topic of Dragon Ball conversation, so here's a little refresher on who Bardock is and what happened to him.
Bardock was a low-ranking Saiyan who led a small group of mercenaries and was married to a fellow Saiyan named Gine, who was also a member of the group at one point. This group would travel from planet to planet to destroy their defenses in preparation to be sold by Frieza. Bardock was cocky, but cared about his comrades and would save them during battle, making him popular with the lower-ranking fighters. He was also one of the few Saiyans to challenge Frieza's rule over his people, something even King Vegeta wouldn't do. Bardock was also shown mourning the deaths of his friends, something rare for Saiyans. Despite this, he was also a brutal killer who reveled in the act of fighting.
Gine, not really cut out for fighting due to her gentle demeanor, eventually retired. This also seemed to have an effect on Bardock, who was famous for his bravery even among the higher-ranking Saiyans. Thanks to Gine's influence, Bardock was more caring toward their children Raditz and Goku, a rare trait for his kind. After learning that Frieza was afraid of the Super Saiyan legend, Bardock began planning to send Goku away from the planet to ensure his son would live. He was successful in sending Goku to Earth in an Attack Ball -- months after this, Bardock and the rest of Planet Vegeta were destroyed by Frieza.
Bardock didn't make his first appearance until the movie Dragon Ball Z: Bardock - The Father of Goku in 1990, so he is a Toei Animation original character. This was a flashback to his confrontation with Frieza and the destruction of Planet Vegeta. In the manga, he made appeared in two panels when Frieza first sees Goku, who reminds the tyrant of Bardock. He would show up again in the Dragon Ball Z anime, when Frieza remembers how he was confronted by Bardock just before Planet Vegeta's destruction. Bardock also briefly appears in the first episode of Dragon Ball Z Kai.
Bardock even received a second special in 2011, in which he was saved by Towa from being disintegrated during Frieza's attack. In this what-if special, called Episode of Bardock, Towa would try to capture Bardock using a wormhole, but Bardock escapes to Planet Plant in the past. Here, he meets a group of inhabitants and saves them from two fighters working for Chilled, Frieza's ancestor. Chilled comes to the planet with his army to investigate the deaths, and he and Bardock begin fighting. Bardock reaches Super Saiyan, defeats Chilled, and walks away into the sunset. He also briefly appears in Cooler's Revenge and is mentioned in Broly - The Legendary Super Saiyan. There's another version called Xeno Bardock -- who is a member of the Time Patrol -- that appears in Super Dragon Ball Heroes, an anime web-series based on the Dragon Ball Heroes game.
He's also appeared in several video games. In Dragon Ball Online, he appears as a mind-controlled servant to Mira, who saved him from Frieza's attack. This version, called Time Breaker Bardock, fights the player during the third Time Machine Quest. He also appears in Dragon Ball Xenoverse in a secret story at the end of the main narrative, and in Xenoverse 2 as an antagonist under the control of Mira and Towa. Bardock also makes appearances in Dragon Ball Heroes and Dragon Ball Fusions. In total, Goku's father is either referenced or appears in 31 Dragon Ball video games.