Oa is a fictional planet at the center of the DC Comics universe, home to the Guardians of the Universe and headquarters of the Green Lantern Corps. The Green Lantern Corps was created by The Guardians of the Universe as an intergalactic police force. The Green Lantern Corps exists to promote order and justice throughout the universe.
The Green Lantern Corps home base of Oa is also featured prominently in "Green Lantern", the 2011 superhero film which just started screening in cinemas. So we cannot mention Oa without mentioning the Green Lanterns. And since no toy of the planet Oa is available, I'll do the next best thing and cover the Green Lanterns instead ;p
First up is Abin Sur. One of the Lanterns of Sector 2814, Abin Sur was mortally wounded when his spaceship crashed just outside Metropolis. Unable to pass on his Power Ring, he sent it to search for a worthy successor. The ring chose Kyle Rayner. This was the DC Animated Universe version.
In the DC Comics, Abin Sur of Ungara was the Green Lantern of Sector 2814 and predeccessor of Hal Jordan.
Together with Kilowog and several others, Arkkis Chummuck was present at John Stewart's trial on Ajuris 5.
Hal Jordan, test pilot and ring-bearer of Sector 2814 was DC Comics' Silver Age Green Lantern, and one of the co-founders of the Justice League of America in the DC Universe. However, he was replaced by John Stewart in the DC Animated Universe. This was done by creators Bruce Timm and Paul Dini in reflecting racial and cultural diversity. During one of the fluctuations in the unstable alternate timeline created by Chronos in the 2050s, Hal Jordan briefly replaced John Stewart, with full knowledge of all events.
Katma Tui was a senior Green Lantern and also the primary trainer of new recruits. Among many prominent members, Katma trained John Stewart, with whom she had a fleeting liaison, as well as Kyle Rayner.
When John Stewart was put on trial by the people of Ajuris 5 for the destruction of an entire neighboring planet, Kilowog was among several other Lanterns who arrived on the planet. In the DC Comics, Kilowog is a former geneticist and the main drill instructor of the Green Lantern Corps, training hundreds of Lanterns over the years, including John Stewart, Katma-Tui, and Hal Jordan (until he was reassigned to Sinestro).
Kyle Rayner was an artist for the Daily Planet, recruited by the Green Lantern Corps after Abin Sur's death. In the DC Animated Universe, Kyle battled and defeated Sinestro with Superman's help.
When John Stewart was selected by the Guardians of the Universe to join the Green Lantern Corps, Sector 2814 was already under the protection of Green Lantern Abin Sur. John was eventually reassigned to another space sector. It was only several years later — following Abin Sur's demise at the hands of Sinestro — that John would return to his home sector. Not long after John's homecoming, he would answer the fateful summons to join six other heroes in opposing the Imperium invasion. In the aftermath of that crisis, John readily agreed to Superman's suggestion that the seven heroes band together as the Justice League.
This is Green Lantern John Stewart as he first appeared in the Justice League animated series.
And this is Green Lantern John Stewart in the later years. The hair on his head is gone, replace by a mustache and beard instead.
Last but not least, Green Lantern Sinestro. In the DC comics, Sinestro was once the Green Lantern of Sector 1417, often regarded as the greatest Lantern in the history of the Corps. In the 2011 superhero film, "Green Lantern", Mark Strong stars as Thaal Sinestro, Green Lantern and Hal Jordan's mentor. Sinestro starts out as Hal Jordan’s mentor and initially he’s quite a heroic figure.
The widow's peak and thin mustache was for some reason originally based on David Niven and that was how Sinestro was conceived for the comic books and maintained in other mediums as well. Sinestro would later become the Green Lantern Corps' greatest enemy.