Leo made his first role appearance in Pantherella as the duke to the Prince, played by Bagheera. Afterward, Leo co-starred Ash, Dawn, Brock and Iago in Ryan and the Beanstalk. He would later reappear with his partner, Benny the Beast, in Kids World's Adventures With The Real Ghostbusters: The Halloween Door. Both would appear in another Halloween crossover, House of Mouse (20th Universal Goodtimes Century Paramount Crossover) with their newest partner, Johnny (20th Universal Goodtimes Century Paramount).
Leo was born to King Samson and Queen Jaina (Who resemble anthropomorphic versions of Mufasa and Sarabi) in Stormwind City in Azeroth. Shortly after Leo's birth, the leaders of the 12 races Alliance and Horde blessed him and King Samsom, and the night elves, led by Malfurion Stormrage, placed a special mark on Leo's neck. It will only come on when it's purpose has been
Shortly After Leo was rescued by the Autobots (Optimus Prime, Ratchet, Prowl Bulkhead and Bumblebee), who were on patrol in Africa after they recived a report of Decepticon activity. Bumblebee brought the cub back to base and Ratchet noticed a birthmark on the cub's neck. It was a dragon wrapped around a sword. Optimus, knowing the this cub could be very important, decides to bring the cub back. However, the Decepticons (Megatron, Star Scream, Blitzwing, Lugnut and Blackarachina) attacked. They were also after the cub, so Optimus ordered Bulkhead to protect the cub at all costs. The battle ended with the Decepticons retreating.completed. Tragically on the same day that Deathwing attacked Stormwind, King Samson was murdered by the twilight's hammer cult while defending the city from the elemental invasion. Seeing that the baby was in danger, King Varian Wrynn ordered Lady Jaina Proudmoore to open a portal to Earth and told Jaina to take Leo with her. She agreed, but upon arrive, they were targeted by a hunting pack of hyenas. The previous battle had left Queen Jaina too weak to save herself, so instead she tried to save Leo. She hid the cub somewhere safe before she was killed by the vicious hyenas.
Afterward, Ratchet decied to take a good look at the mark on the cub's neck. He tells the other autobots that he was the chosen animal who was marked and in a time of Earth and Azeroth's greatest need, he will rise and defend the two worlds. Knowing the Decepticons would destroy him, Bumblebee suggests that they find the cub a new home. On a clear night in Manhattan, the Autobots left him at the entrance of an abandoned underground research facility, now dubbed "The Labryinth," it was a home for the homeless people of the city and the domain of the Mutates (Talon, Claw and Maggie). Leo was taken in and adopted by Talon and Maggie, and raised in the care of the Labryinth Clan in Manhattan. Despite the damp and dark surroundings, Leo learned to live with it. He enjoyed talking with the other people that he shared a home with, especially his Uncle Claw, who hadn't spoken since his transformation. Leo grew into a handsome and caring lion, and his first steps above ground gave him the sensation of opening up a whole new world.
Later on, Leo stumbled upon the El Arca big five (Xiro, Kairel, Bruma, Panthy and Dagnino), and afterward he befriended a lonely beast named Benny. Both were entering in a film festival, but Leo felt so bad for Benny when his film was rejected that he entered the beast's film instead of his own. It was this simple act of kindness that won Leo a best friend for life. He was also introduced to the Madagascar Crew, who would work with Leo and for Kids World's Adventure Series.
Shortly after, Leo took Benny and the El Arca Big Five on a trip to Africa, where they met a meerkat named Timon and a Warthog named Pumbaa, They also met two abandoned lion cubs named Simba and Jondugu. Leo and his friends helped Jondugu and Simba claim their rightful places in the world.
After they returned home, Leo, Benny and Jondugu (who changed his name to Johnny) became partner film directors.
- Leo, Benny, and Johnny set off on their own adventure with their friends in Kids World's Adventures Series.