The original '90s Young Justice series quickly distinguished itself from the nominally similar Teen Titans franchise, which often told fairly dark, mature stories by embracing a more lighthearted and zany approach. This was best exemplified by the decision to add Lobo to the team shortly after he met the team in 2000's Young Justice #20, by Peter David and Todd Nauck.
The ruthless intergalactic bounty hunter had recently been transformed into a teenage version of himself and quickly became Young Justice's wild card. While Lobo brought his trademark wild antics to the series, he also went through some significant developments of his own.
After being transformed into the teen version of himself, dubbed "Li'L Lobo" by Klarion the Witch Boy, Lobo attacked the latter, hoping to force him to change him back. This led him to encounter the temporary Young Justice replacement team that was filling in for the original squad while they were on a leave of absence. Flamebird convinced Li'L Lobo that being a teen could be an interesting challenge, after which he gave up his vendetta against Klarion. Li'L Lobo unofficially joined the original Young Justice team in Young Justice #25 by Peter David, Todd Nauck, Larry Stucker, Jason Wright, Digital Chameleon, and Ken Lopez. As the team was departing for an outer space mission, Li'L Lobo secretly boarded Impulse's spaceship. Lobo quickly bonded with the team but tension arose between him and Robin, who strictly adhered to Batman's no killing rule.
When Young Justice found themselves on Apokolips following the "Our Worlds at War" event, they were attacked by an army of Parademons and taken captive. Determined to rescue his teammates, especially Empress, for whom he had developed an attraction, Li'L Lobo single-handedly fought through a massive number of Parademons but was eventually killed. The large amount of Lobo's regenerating blood that was spilled grew into dozens of separate Li'L Lobos that rescued the team from the forces of Apokolips. One of these Lobo duplicates was smaller and weaker than the others and piloted Young Justice's ship to safety. He came to call himself Slobo, after mishearing Secret say "So Lobo", and took Li'L Lobo's place on the team. Slobo initially struggled with self-acceptance as he was ashamed of himself for not charging into battle with the other Lobos but he went through a lot of growth during his time with Young Justice and ironically enough came to function as something of a conscience for the team, despite claiming not to care about morals.
Slobo continued to appear in Young Justice for the remainder of the series. In the final issue, aware he was dying, Slobo bravely charged against Darkseid after Secret was freed from his influence before being blasted by the New God's Omega Beams. The team believed Slobo died but he was actually transformed into a statue in the headquarters of Young Justice One Million in the far future. Although he was aware of his surroundings, he was unable to move, speak, or do anything else. The Li'L Lobos left on Apokolips eventually turned to battle one another until only one was left, who then grew back into a regular adult Lobo. When Lobo later encountered Robin and Wonder Girl once more it was confirmed that he no longer remembered his time as a member of Young Justice.
The adult Lobo is a recurring antagonist in the Young Justice animated series, and the show's third season it teased the possibility of an appearance by a version of Li'L Lobo or Slobo. When Lobo battled Nightwing's covert superhero team his finger was cut off by one of Halo's energy blasts. The credit sequences of several episodes then showed the finger continuously changing form, apparently in the process of regenerating. The season finale, "Nevermore", featured an after-credits scene in which the finger had grown into a horrifying baby version of Lobo. But the adult Lobo promptly arrives and squashes the clone to death before lighting its blood on fire with his cigar to prevent any more regenerations.