For those who do not know, Planet Hulk is an adaptation of the popular Planet Hulk story line in the Incredible Hulk comic books. Like all adaptations there are several changes made to the animation that either did not happen in the original story or was slightly altered for whatever reason. Ultimately, some changes worked well and other fell far short.
This incarnation of Planet Hulk is very close to it's inspiration. No longer able to tolerate the Hulk's rampages, a group of superheros (including Iron-Man, Dr. Strange, Reed Richards and Professor X) decide to capture the hulk and rocket him to another planet where there is no intelligent life, plenty of game and all the peace and quite the Hulk has always wished for. Not a bad plan if the Hulk's ship actually made it there – It seems the greatest minds in the Marvel Universe didn't account for the possibly (or should I say inevitability) that the Hulk would break loose inside the ship and send it off course. This change in course sends Marvel's mightiest mortal through a worm whole to the war planet of Sakaar were the Red King ruthlessly uses the populace (and any stray aliens) as fodder for his gladiator-style games. Captured and controlled by a "control disc" implanted in his chest the Hulk is quickly taken to the Maw (the planet's massive gladiator arena) to fight monsters alongside other imprisoned fighters. Eventually, the Hulk decides to join the 'warbond' with his fellow gladiators to overthrow the Red King despite his reluctance to care for people he knows will betray him sooner-or-later, just like his former friends on earth.
This is where the animation starts to veer the farthest from the original. For whatever reasons the creators of this DVD chose to make two major story changes that take away a lot of the emotional power that the comic book storyline had going for it despite the rather clichéd gladiator plot. It will come to little surprise that in the end the Hulk defeats the Red King, Marries the warrior princess and becomes king himself. Pretty standard ending in this genre story, but below is what was left out.